1. The main concern of a clutch situation should always be the time factor. Depending on the time left for the round, different strategies can be applied to turn the odds to your favour.
2. Never plant the bomb and give away your location if you have enough time left. Instead wait in the most probable path of rotation to get some free frags. However if you have very less time left, its always best to put the bomb down, as it fetches your team members an extra 800 $ each.
3. In maps like de_nuke, spam to cause distraction by sounds and give a wrong impression of your actual position. For eg. you can break the ducts by spamming the upper floor and make the opponents think you are in the lower bombsite coming out of the ducts while you are actually in the upper bombsite.
4. Remember that the sounds of picking up the c4 and any weapon is almost identical. So if you see the bomb dropped, you can drop your weapon and pick it up again and wait for the defender to peek, who would think that you picked up the bomb and probably turned back.
*5*. Try to make as less noise as possible. Techniques like silent run are best in these situations. And always try to fool the opponents by making smart use of sounds. For eg. the breaking of lights at the ramp in de_nuke make a sound identical to breaking the ducts. This would distract the defenders making them to expect you coming out of the ducts instead of the ramp. Also the chucking of a smoke grenade makes a similar sound to that of a flash grenade. you can throw a smoke to make the well positioned defenders to turn away thinking that it might be a flash and you can peek to get the exact position of the defender..
7. Defending a dropped bomb in a 1-o-1 situation, dont peek the moment you hear your enemy pick up the bomb. Wait for a second and you will get him by his back instead of a crosshair waiting for your head to peek. In a 1-o-2 or more situation, dont stay near the bomb,instead stay in the path where they are likely to go after picking up the bomb.
8. Always make sure to change your positions if you get frags one by one as the dying person may spot you before dying and convey the same info to his team-mates before his screen goes completely black.