As Ghost:
Try getting melee's other than the knife
Right click first and if they dont die slash
Aim for head
Bunny hop, dont move if your not bunnyhopping
When you see an enemy, move! Dont sit there
Use C4 Plant speed increase, breath down, footstep down
Try to get to know the maps, find hiding spots
Be fast
Work as a team
Stay near bomb
As a human:
Use silenced weapons or shotguns
Wear headphones and turn up volume to pin point
Turn gamma up to 100
Move around alot, run and jump
Use cf defuse speed up
Have a secondary
Use smoke grenades
Work with your team
And look for ghosts