Red Dead Redemption

Join a public free roam and then invite a friend. Posse up and then create a team deathmatch or any other team based game mode.

Now, when the match starts, have your partner leave, which automatically nets you a win.

Now when you go back the voting lobby, invite your friend to the game again and when the next match begins, do the same.
After your partner leaves the match for the 4th time, you will get the achievement.

PS: make sure you kick whoever joins the match because for a small window of time you and your partner will have the majority guaranteeing the unwanted player is kicked.
This shouldn't really be a problem since the method takes mins and if you are in a fairly empty free roam, the chances of people joining your game are pretty slim.

Go Team...sounds like it is a daunting task. I mean win four in a row? That is pretty tough! Actually it is very simple!

What you will need for this is one boosting partner. I chose one of my buddies on Xbox Live. This will take you about 30 minutes for both of you to get the achievement if you play Capture the Bag as your gametype.

What you will need to do is start up a Public Free Roam session. While in the session invite your boosting partner and meet up in the town of your choice that has a Gang Match marker. I like the town of Armadillo because it is small and has visible markers. Once both of you are in Armadillo make your way to the Gang Match marker. Make sure your friend is standing next to you by the marker. Start a Gang Match and have your friend join it. Once you see both of your names pop up on the upper left hand corner start the match by holding down the Y button.

Now most of the time since you were standing right by each other at the Gang Match marker you will be thrown into your own match. Wait for your boosting partner to show up then vote on your favorite gametype. Once the gametype is chosen immediately start the match so it is just the two of you. I prefer playing Capture the Bag because you only need to capture the bag 4 times for your corresponding team. On the town of Armadillo it is setup so at one end of the street there is one drop off chest/goldbag for each team. This is easy because all you do is run back and forth down the street to pick up the other team's gold bag and then drop it off at your chest. Drop off the bag 4 times and you are done.

After the match vote to play it again. Once gametype is voted on again start the match as quick as you can. Other players can join in at any given time so be sure to give them the boot! This is known in this game as Vote to Kick!

Being that this is team based, and multiple players can join in at once. Have your friend grab your bag of gold and tell him/her to go hide it, or have them protect your own chest with some team killing tactics. In this game type your team's bag does not even have to be in the chest for you to capture the other team's bag. Your friend helping you in this matter is great if you don't have time to vote to kick or if there are too many people that join up in your game session.

Not many people will join in because if they have a big posse they will get matched up in some other match. If one person joins in they will be easy to kick. Usually no one else will join though and you will be fine. Remember these wins have to be consecutive and you need four of them. If you dashboard out or get disconnected from your game session then you will have to do all four of them over again. Don't get discouraged if others join and mess you up. It also helps to do this late at night.

At the end of your 4th game you will be getting the Achievement and shouting Go Team! Wait a minute I thought no one else was on your team? Oh well! Atleast you got the Achievement!

1. Get a friend and make a posse in public free roam.
2. Go to the nearest town with the Gang Matches Icon.
3. Both of you hit Y on it to enter a game.
4. Once in the game, leave the posse so that you can start.
5. Vote and skip to HOLD YOUR OWN game type (I did Chuparosa). This game type is faster than Grab the Bag by 40-50%.
6. Vote to Start the game.
7. Have one person capture the other person's bags three times to win (approx 3mins per game).
8. VOTE TO REPLAY
9. Do this 4 times (approx 15mins total per person)
10. Kick anyone else who joins (rarely, if ever, happens).

There are some good solutions if you want to boost for the achievement, but personally I like to try and limit my boosting to games where that's the only option.(due to dwindling online communities etc.) So assuming there are others who would prefer to attain this legitimately I figured I would post some useful tips for playing multiplayer.

I got this while playing regular gang matches which consist of 2 types of game modes: Team death match, and an objective type game mode called grab the bag.

General Tips:
Dodge.
-Take full advantage of the limited evasive abilities at your disposal.
Perform rolls by holding LT and tapping X+the direction you want to go. Keep in mind that rolling is limited to 1 every few seconds, so try to use them wisely.
Pressing RB while running toward a wall or other environmental object will cause you to slide and take cover on said object. This slide can be useful for quickly getting out of enemy fire, just be aware that the cover mechanic can be a bit sticky.

Upgrade your load out
-The weapons you spawn with tend to be very weak, however wherever there is a gun icon on your mini-map, there is a blue box which contains stronger weapons. You will need these if you hope to win. Specifically you'll want to learn and memorize the locations of the High Powered Pistol. This gun destroys, and is not only powerful, and fast but has a huge ammo capacity.
There are a couple other good weapons in these boxes such as the Evans Repeater, and Semi-Auto Shotgun, but I personally tend to stay away from using shotguns because in my experience their range and seemingly weak power make them easily outclassed by handguns or rifles.

Know thine self
-Depending on the faction you start with your starting weapons will vary. Always take time at the beginning of your match to check what weapons you have available. Some times you'll start with a sniper rifle at your disposal, other times dynamite. Utilizing these effectively will work to your advantage.

Head for high ground
-Many if not all the levels have areas where you can climb up to get a better vantage point of the area. Very often if not always, this is the wisest position for you to take. You'll be harder to kill, and at the same time have an easier time finding unsuspecting fools running out in the open.

Don't be an unsuspecting fool!
-You just read about how easy it is to kill idiots running around through the map. So don't do it! Sweep the outer edges for stragglers and head for high areas with good vantage points and available cover.

Double Tap
-Do not expect online enemies to die as easily as one from the campaign. Even a well placed head-shot sometimes isn't enough to finish the job. That's right you heard me, your enemies are harder to kill then zombies. Fire your weapon and don't stop until you're sure they're dead. Trust me when I say it can some times take a LOT of bullets to put someone down.

If you can't be the best, befriend the best
-Even after learning the multiplayer enough to stop dying constantly, I had a bit of a tough time getting 4 wins in a row. I hit 3 wins and then lost on the fourth at least 5 times >:(
My remedy? Play smart. Send Posse invites to whoever is in your game dominating. If they accept, you will always be placed on the same team, ensuring victory. You may wonder why they would accept a posse invite from a random person, but it seemed to work for me. All it took was one really good player to join my posse and other good players followed suit after that.

That pretty much concludes my tips. Hope you'll find them helpful.
Good luck partner.
Got any good tips I didn't include? Post em' below and help me better the solution.

It's the same as atOnz said, but here, a video guide showing how to do it.

It's pretty easy with a friend, but if you try going for it in the right way, like, winning 4 times with your team on a normal match, it's VERY hard, believe me...

PS: This can be done with The Quick And Everyone Else... achievement as well!

*This can be done with a minimum of 2 people.*

This may not be the best method to do this achievement, but it is certainly worth mentioning.

First off, it is unnecessary to be in a Posse together. This will help with the chance to find an empty lobby.

1. Hit the Back(<-) button and select Legends & Killers Free For All
2*. Keep doing this with your friend until you or him get an empty lobby, and whoever gets it first needs to invite the other.
3. Immediately start a game by having both players select Ready.
4. Finish the shootout in the beginning (This cannot be skipped).
5. Have the person who is not getting the achievement leave to Free Roam.
6. The match will automatically be won. But you need to immediately open the Xbox guide and invite your friend back into the game while the post-game results are still being shown.
7. Repeat steps 3 through 6 until the achievement pops.

This method also works for the following achievement:

But it is necessary for you to select Legends & Killers Gang Matches

*Part of the reason you do not want to be in a posse together when you start this is in the case that you do end up with randoms joining you for "The Quick and Everyone Else", the game should always put you on separate teams, which you can use to your advantage. Friendly fire is on...

*Also if you do have 3 people working on this at the same time, you can vote anyone who attempts to join the game.

This solution is an alternative for those that do not want to get this achievement by boosting it. TrueDevilHunter posted a very good legit solution earlier on the guides. Read that solution in addition to this one for great tips on getting this achievement.

Time of Day
I found it much easier to win gang matches very late in the night or early in the morning. Primarily, this was because the number of players tended to be lower which allowed a more stealthy, strategic game.

Play to Your Strengths
From playing various MP shooters I see two primary styles of gameplay. There are those players that are super fast and move around a lot. They tend to get the most kills but also die a lot as well. Then, there are people who prefer to be sneaky which results in less kills and less deaths. Personally, I am of the latter type. Use your strengths and practice, practice, practice. For example, in Hold Your Own games if you are a sneaky player go hide out by your treasure box and kill any intruders. Also, if you are a player that has a low K/D ratio in shootouts stay hidden so you don't boost the other teams score.

Keep Swimming
If you want to get this achievement without boosting, it is going to take you some time. Keep playing gang matches over and over. You will learn who the best players are. In my experience, if I was stuck in matches where the best players were all in a posse together this was a waste of my time. So, once I realized this was the situation I would exit out of Gang Match and reenter to get a different batch of players. Keep doing this until you get a batch that does not have a "super posse".

Posse Up or Not...
There are two strategies that you may find useful using the posse function. The first was outlined earlier by TrueDevilHunter where you find good players and send them random posse invites and make your own 'super posse'. The second strategy is to avoid getting in a posse. This is for two reasons: 1) If you join a posse and they suck you will be stuck on their team in all matches 2)If your posse leader leaves the Gang Match you will leave with them, ruining your streak.


General Notes
If a match ends because all players left except the ones on your team, this is considered a win.

Good luck hunters!

Just want to do an update for anyone still looking to get this as of April 2014.
The MP is still hacked but you CAN still get this achievement.

Follow Faris Hilton's solution:
Then when the hacked MP freezes on the loading screen -
have your partner quit to dashboard.
(Your partner must quit to dashboard, because once you're in the frozen loading screen, it is the only way to quit.)

This will automatically net you the win, and you'll be returned to score board.

Re-invite your friend to the lobby (kicking all randoms as quickly as possible.)

Do this 4 times with a partner and you got the achievement.
(remember to kick all randoms as they will extend the frozen loading screen in till they quit to dashboard themselves.)