Game Information
The smoke grenade is ideal for taking cover.
Snipers tend to use the smoke grenade when trying to escape their sniping spot when under attack from the enemy.
It's also a great idea to throw the smoke grenade at one entrance, distracting the enemy, which would then allow you to use a different entrance and surprise him.
Be aware that when you are in the smoke, your PSN ID will NOT appear above your and your teammate's head and can sometimes cause confusion, and if on Hardcore mode, could make you team kill as a result of this. Some people set off a smoke grenade purely because of this.