Aliens vs. Predator

First off, the easiest mode to get this on is Infestation. Mainly because if you have the right strategy, and are confident in handling aliens en masse, your score will go up very quickly.

For a particular strategy, I recommend is Gateway (Thanks Guirec730) the one with the crashed space ship and the marine compound.

Anyway, go to the crashed space ship across the ledge is the sniper rifle, camp there grabbing regen ammo till you have something ridiculous like 50 sniper bullets. Of course this will not be quiet and you will most likely draw in some aliens, so try to stay alive.

Now when the numbers start dwindling head over to the mouth of the cave, and camp at the top of the mound. Most players arent too smart and will just run up the mound, so gun them down with the sniper rifle.

Check the cave periodically to make sure you wont get ambushed, although not many people take that entrance so concentrate more on the compound. It will take a lot of tries and luck, but you will get there in the end.

Good Luck :)

Easy to do as a marine, particularly in a domination match with a team to play with. Camp a spot as a group and have your team help weaken aliens for you to finish them off.

Most alien players jump at you with a weak attack which you can simply block, counter, and then shoot them on the floor for an easy kill.

A useful note is that i actually had a 'recorded' killstreak of 8 for the match i got my achievement in, however, i accidentily killed 2 team members during that streak - so team kills do count toward your killstreak achievement.

I don't encourage team killing, but if you are having trouble every little helps i suppose...

The best way I found to do this was be a predator and just lay 100000 mines (you can only lay 5 at once) then hide and hope aliens dont find u, and boom marine guts everywhere :D. Also temple is the best level as you can trap the archways

I actually got this whilst boosting Persecutor Complex achievement with a buddy (see my guide),if you boost that achievement and the 3rd player dosent find you then you will easily get 10 kills in a row.
I found that not a great deal of people are playing this online now (especially Deathmatch) but bear in mind that you need a minimum of 3 people to start a match.
So just sit in a lobby with your boosting buddy and wait for 1 more player and then start game.
Hopefully noone else will join (they didn't for us) and with a bit of luck you can communicate with each other and stay away from player 3.
Bear in mind that if player 3 does find and kill you,it will obviously reset your kill count.

Ranked infestation is a good bet here i found it easy to get a kill streak going but you have to react fast and its best done as the marine ofcourse i just grabbed the grenades and the shotgun got 9 kills but 1 guy have to sneak up on me its fairly easy.

I found that if u choose the marine on map temple(cant remember exact map) and take the shotgun and when in close quarters it destroys the enemy but be careful against aliens because of the acid.Predators generally die straight away.Hope this helps