When you play any game type where you have to plant a bomb
Search and Destroy
Hardcore Search and destroy
When you are planting its good to trick the enemy. When you are planting the bomb you press keep pressing L1. You will then throw a C4, even though you dont have it on your Perk 1. I would go with a setup like this.
Any 2nd gun
This is a good idea because when you have planted the bomb you can do the C4 glitch and throw the C4. Then you plant your claymores. The enemy will automatically see that the bomb is heavily armed with explosives.
So it will take them longer to defuse because they will havae to look around the area before defusing. IF your dead.