Ok, random thoughts from a man, trying not to be in any way graphic:
the best tip I can give is just think in terms of "up". By that I mean, the more blood at the top of the penis, the fuller it feels to the man, the more pleasure he will get and the better the orgasm. Just keep the blood flow rising upwards, using whichever technique you feel comfortable with.
Always roll your lips slightly over your teeth to avoid teeth rubbing on the penis, that is such a no no!
Don't suck tooooooo hard and never blow!
Also nothing wrong with asking if he is liking what you are doing. We are all different and respond differently to different things.
Also the starting a fire technique works well. i.e. rub the shaft between the palms of both your hands, like when you are trying to start a fire.
Also also there is no doubt that the more of the shaft you can have in the mouth, the greater the pleasure for the guy because he is benefiting from all the different textures and feels of a mouth i.e. lips, tongue, cheeks, if that makes sense! I don't mean performing sword eating feats, just enough to be comfortable.
Rhythm is very important. Don't just go full pelt and by the same token, don't send him to sleep by being too slow for too long. Change your rhythm according to the physical feedback you get from your partner i.e. noises, clenching of thighs, arching of back etc
Finally it's very sensitive down there, try and avoid friction, keep it as lubricated as you possibly can and don't grip or rub too hard for too long.
Hope that all made sense!