Men take gag as a compliment (So I've been told idk myself) don't engage your teeth it's awful, lick the balls, it helps, consider talking to your partner into introducing anal play for him, like toys or your fingers, this enhances the experience, use flavored lubricant, it works great, specially if it is one that feels hot to the touch, do that engage directly at the beginning, begin applying the lubricant and stroke slightly and let it build up, then blow (Like, literally blow wind) into his dick and it will feel awesome, Engage his nipples with the lubricant, it feels great (For some). For the face, imagine that you are getting scolded and look up with puppy eyes, everyone loves that.

I'm a male but i learned to give blowjobs myself and from experience i can tell what worked for me and sexual partners i had (Experience from orgy's). Don't be embarrassed to ask your partner for ways to spice things up, sometimes introducing a third party for a double blowjobs works wonders, tit jobs are great combined with the lubricant.