As a general advice, start consciously fixing your micros until you internalize it (don't have to think about it). Everyone knows that you need to have good crosshair placement, movement, strafe-tapping, bursting far ranges, not crouch spraying close, etc. However, most low ranks who know about that still has shit micro.
Whether you are holding an angle or are about to take a gunfight, psyche yourself and make a fast checklist. That is what I mean by consciously fixing your micros.
For example, if you are holding an angle, consciously make the decision yourself to correct your mouse to head level and if you will be bursting or spraying and concentrate. Concentrating is important as bad players tend to drift their mouse elsewhere especially if they are thinking about something else like teammates.
After a certain (long) point, you won't have to think about crosshair placement or how you will engage in a fight. Your experience will be internalized and your muscle memory will do what it needs to do.