Help with what? Gaining more XP?
There's pleny of pointers and tips to be given, but I don't know how good you are or how much you know, so I'm just going to throw some things out there and hope you find them useful.
-I've found that the fastest and easiest way to gain XP is playing Headquarters. You have the potential to get points without even doing anything, as long as your team is good. Plus you get extra points for capturing and destroying the HQ and obviously killing opponents.
-Make sure you check your barracks often to see what challenges/weapon challenges you could be working on.
-Also make sure you have the right perks to go with the right gametype or weapon you are using. Example: Don't use "stopping power" with a shotgun, because the shotgun already has tremendous power. Instead use "double tap" so you can fire the already powerful shots twice as fast.
-Obviously, you don't want to run out in the open unless you absolutely have to. You want to be constantly moving around (but take it slow, be careful around every corner) because you want to find someone before they find you, and if you camp in one spot it won't take long for the other team to find you.
-Lastly, just practice. The only way you can get better at something is to do it more often. It's also helpful to play with people who are better than you. As much as it sucks to get pwned, it's one of the most effective ways of learning new and better strategies. You get to see firsthand all kinds of different strategies, then you can try them out on your own and find the one that works for you. If you want, shoot me an email with your gamertag and we can play sometime. thamm89@yahoo.com