My favorite is a technique my wife and I worked out to get me to cum (I couldn't during a standard BJ) without gagging her.
She lies face-down on the bed, propped up on her elbows, facing the edge.
I stand facing her. The bed height is perfect to match my cock with her mouth.
She goes to work with her mouth, and her fingers.
When I'm ready to go the distance, I start thrusting my hips. She adjusts her position on the bed so that when my thighs touch the mattress, I'm just short of gagging her.
Then I can throw my hips as hard and fast as I need to, and she simply takes my cock in and out of her mouth.
We call it a "mouth fucking." Definitely worth trying if you can't cum from oral. Or worth trying anyway.