If you're good try HC SnD. I dont like headquarters too much because I usually find games that are halfway done and I am on the losing team. It hurts my KD.
This too actually works, play with a about 2-3 good people you know, and have your team just hold the bomb, don't plant it, just make sure the other team doesn't either, and just kill as much as you can, and you will kill a lot since games are 20 minutes long. Best game for me: 76-19 on Courtyard. I made about 1300 points.
I play HQ, If you have a good team of 6, 5 friends and you, you can capture the most points say 200, in the first 5 mins, get those points, then dont capture the HQ and try not to let the other team 2. This way you get 5 points every 5 seconds whilst the HQ is captured up to 200 points, then 10 mins of killing getting 5 points for kills. I average about 1000 every match, before challenges. Think bout double XP, 2000+ each game.