Make smart use of the laser sight on your weapons. It's useful for aiming at a certain distance, but it can also reveal your enemy location. Hide your movements and the noise you make, silencers will be your best friend. Use the weapons that are most useful according to your level. If you are a beginner you should use the easy to use masses to make it easy for you to progress through the game until your skills have improved. Lastly, keep in mind the roles on the battlefield. Depending on your play style, there will be weapons that are better suited to your play style.