I have been using this technique for years, and I still enjoy it.But it may not be to every one's taste.
Start by being naked. You can lay on your back a bed or on the floor. On a bed, your head should be close to the wall or head board. If on the floor, a wall or a couch or chair. A pillow under your head is more comfortable.
Play with your cock and balls for awhile and get hard, get some precum flowing. When you are really hot, and getting close to cuming, raise your legs up over your head, so that your cock is directly above your mouth and face. The closer the better.
Slowly keep stroking so that precum drips down to your face and mouth, catch some on your tongue and tast. (I said that this may not be to everyone's taste.) When you feel yourself cuming, aim for your mouth, (if you like to eat cum), or just your face, and let your cum flow all over.
I prefer to catch as much in my mouth as possible, and swallow very slowly.