You must finish first place overall in points, regardless if you win or lose, in 20 different matches. This is an accumulative achievement, and since you have to play 500 matches overall to win that achieve, most likely you will net this one too. Here's some tips.
In Conquest, make sure you capture and defend the flags earnestly. You earn extra defend points if you do. Taking out vehicles also earns extra points. Never camp or wait for action, go create it!
In CTF, go for flag captures or defends. You can get up to 7 points per flag capture if you pick it up and score it. Do that several times and you'll easily have the lead in the game.
The community that primarily plays the game now are boosters and hardcore players. If you lack skill, try getting with the boosters to earn the achievements. If you want a good challenge though, have fun with the die-hard pros!