I know your level is based on your score alone. So the key is raising your score, which also drops. It took me quite a while to get to 2000 pts to get lvl 5. Seemed like every time I'd get over 1500, I'd have a bad game and go back to 1300. I think the biggest contributor to your score is simply being on the winning team. Even if you were number 1 on your team, I don't think you get many points for it if you were on the losing team. Try to keep your kills higher than your deaths obviously. Or at least close. With the way people kill you (me) so fast other game modes can nab you alot more points than sharpshooter (team DM). I noticed I got a huge pt boost after a game of domination, and I had very few kills. Just grabbing objectives. Hamburger Hill is good for that too. But not many ppl play those modes for some reason. I think they are fun. Battle is good for points too, but I HATE battle. Hope this helps a bit.