Anyone got tips? I know the achievements give you a ton of XP, but other than that, I know that getting top 3 and a ton of kills is the best way to get XP (well that's the method I'm doing).

Are objective games better for XP?

Weapons gives bonus exp as well for certain amount of kills.

Level up your modules. The XP bonuses for them are really high. And if you are good play instant action as you will get alot of xp and kills most rounds.

I would suggest Team Instant Action on Fast Rounds.

You can also play Crash Site or Capture the Relay but you will need a good team to have good tactics for them.

capture the replay is good for xp especially if you find a boosting lobby. just lay low let them boost and boom start shooting and grenading rack up some insane legit xp without the need for boosting also it annoys the hell out of them lol

TIA or Assault

IA is the best IF you can consistently win, you will get 4500+ XP per 4-5 mins (per match). Also you will upgrade your modules fast as you will mostly get the vast majority of your kills using your gun.

Rohan is right, TIA Fast Rounds is really good, I think this second is best for xp. I think this because you have to compete with other good players (there not that common) for kills.

Like Portly said level up your modules for bonus xp and attachment. Use the laser and the Assault scope, you only need 100 kills with each for 5000xp which is a lot. Don't listen to everyone's nonsense about the laser being visible when your stealth you can't see it and the more enemies that do see it the more kills for you if you're good.

capture the replay is good for xp especially if you find a boosting lobby. just lay low let them boost and boom start shooting and grenading rack up some insane legit xp without the need for boosting also it annoys the hell out of them lol
LOLZ.

I don't appreciate boosters...

neither do i its so funny when your in there gaming killing them