Map knowledge is pretty much key to being good at this game. I find that once you know where the spawns are in different game types you can easily pick off enemies when they don't expect it.

However to be one of those players who gets a moab every other game, I'd say it's more down to team effort. If you're playing in a team who know how to manipulate the spawns so that the enemy spawn in the same place over and over again, you're at a great advantage.

However, if we're talking about free for all, it's pretty much down to map knowledge. Staying in high traffic areas and keeping an eye on lines of sight.