How the hell play MG?

I know I should be like 100-300 meters from the enemy. But finding a position is difficult.

When I find a good position - no enemy. When I know where is enemy, getting to the good position usually gets me killed. When I find a good position with enemy - as soon as I start blasting I get a headshot.

Should I shoot just in their general direction? Or try to target individual enemies? Shoot through the smoke? Does short bursts matter in this game?