Find a Team & Communicate
If you don't already have a team to play with, you'll want to track down some players in-game or through the Call of Duty Reddit.
If you have friends playing the beta, group up with them. A little communication and teamwork can go a long way. If you don't have friends, try to group up with some players that compliment your style of gameplay. Who knows, maybe you'll find a team that carries over to the public release in November.
If you have a team that works together, Call of Duty becomes a lot more fun and enjoyable. So, take stock of your opponents and comrades and see if you can band a group together to take on the various clans that are already out there.