Gears of War

Boosting Method for this:
Get a party of six (Gaming Sessions are usually your best bet)
Have the host set up 1 round on Garden in Warzone, as its not a very popular map you should be ok finding each other.

When the game begins everyone should run straight in to the greenhouse at the start to suicide.

Even tho you get the message that the last player disconnected or suicided, the game is still counted as 'completed' this is by far the easiest and quickest way to get this achievement when boosting.

These games take about a minute in total. In fact it takes longer for everyone to actually get in the game than it does to complete.

I boosted this tonight and 3 or 4 of us all got this achievement using this method.

This was always near impossible back in the day if you were in the UK, however I started this a few nights ago (April 2010) and have now unlocked it. War Machine, on Warzone, 5 rounds, 3 minute timeout - people will jump in.

I unlocked this in the same game were the entire opposing team eventually disconnected, so "complete" probably just means don't go quiting, as host you need to see it out.

all you need to do is host 50 ranked matches to make it go faster host it on raven down something like 3 rounds so people will join because nobody will join a match if its only 1 round

This achievement can be very hard to attain on your own. When you set up a match it can be hard to get others into it if your the only person in the lobby. A key here is to have a friend or two play with you.

Randoms that still play the game look for matches that are close to starting. If you set up a match tell your friends what map it is and the set amount of rounds.

An easy way to distinguish your map from others for your friends to see is the round duration. Set it at a odd time such as 9 mins or 12 mins.

Popular Maps
Gridlock
Canals
War Machine

This achievement can be easily gained while boosting Seriously, or if you cant be bothered aiming for seriously then a 3-5 round match on War Machine or Gridlock will unlock this achievement quickly. Do not worry if people leave during the matches as long as they are completed then thats all that matters.

i just got this achievement the other day...if people quit out of your game it will still count towards your achievement progress...Just make sure you write down how many games you hosted. I dont know if anybody else said that on here before i did. But i m just letting you guys know...Good luck

As of August 2019. The servers are averaging less than 200 players a week. So if you're new to Gears of War. It's a anxious time to be playing with Gears 5 just around the corner. shinyshirthero's guide works fantastic. There's no fault with that but because of the player traffic here's the boosting method for maximum efficiency:

War Machine
1 Round
1 Minute
6 Players. 3v3
"The Buddy System"

Each team will have a Short runner, a Long runner and a Torque/Middle runner.
Player 1 - Short
Player 2 - Torque/Middle
Player 3 - Long

Both team's Short runners will run to their grenade spawn and pick up the Frag Grenades. Stand by and wait.

Both of the Long runners will run to the opposing team's grenade spawn.

Both Short runners will then Frag Tag the opposing team's Long runner. And stand next to each other. Both dying from "Enemy Frag Tag explosion".

The two Torque Bow runners will run to the Torque Bow (in the middle, between both Frag spawns). Either Middle runner can pick it up but keep it consistent to one person. The guy with the Torque Bow will shoot the enemy, sticking them. Then stand as close to the enemy as possible. Both dying by "Enemy Torque Bow explosion".

The game ends with everyone having a kill and a death, either team can win.

Now for those wanting a Chainsaw kill. It requires a little more coordination.
Chainsaw Killers can only be either team's Player 3 - Long runner. As they are the one being Frag Tagged by enemy team's Player 1 - Short runner. Once the Frag has been tagged. Chainsaw the opposing team's Short player and you both will die. One from Frag Tag. One from Chainsaw. You have a very small window for this.
This will NOT work for Torque Bow/Middle runners.

So there you have it!
A Series of Tubes
It's a Massacre
The Nudge
Is It a Spider

All in one simple session, this is also the very same method you will be using later on in your Gears Career to "Suicide Boost" very fast. Very efficient. Now you can boast that your good friend Rad has shown you how to start grinding!

This method will net you 300 kills towards Seriously with your party of 6 and get you at least 2 of the 3 achievements depending on how fortunate you are. Each match will take about 25 seconds and just as shinyshirthero mentioned. You'll be spending more time searching for games or dealing with random people joining than actually playing. Switching roles is very easy. Just make sure you and your buddy. Switch with another pair.