I think it's considerate and common decency to make sure you're absolutely clean before engaging in sex. It's also sooooo much sexier when you know the other guy is clean and has nice breath so you feel comfortable kissing him and licking him everywhere.
Firstly, I shower and make sure every inch of my body has been washed. Especially the penis/ass area and the sweaty regions (neck, armpit, back, chest).
Secondly, I brush my teeth, floss and also use mouthwash to keep my mouth fresh.
Lastly, I think it's also really good to drink some water and keep yourself hydrated because having a dry mouth can cause bad bread / bad saliva smell. I also use some "clean" smelling colognes on the neck and body to keep myself smelling nice. I recommend Cool Water by Davidoff or Green Tea by Elizabeth Arden. These are relatively cheap colognes but smell so clean and amazing.
Hope it helped and stay clean!