Breath in though your nose helps for me 

If you hold one hand (preferably not one that is around a penis) in a tight fist it can reduce your gag reflex. As for the taste I don't typically mind it, but if for some reason it's bit pleasant one day I'll try to "aim" it toward to back of my mouth so it's not on the forward most taste buds. Typically, for me at least, the taste isn't a noticeable then. 

Give oral in the shower you won't really taste it and just spit out

I love the taste so that's not a problem for me - just try not to think about it too much, or focus on how much he enjoys it to distract yourself. I breathe through my nose and take breaks from using my mouth when my jaw gets tired. 

Get throat numbing spray!! It actually works. Also for the cum, have it shoot down the back of your throat so it bypasses your tongue and your taste buds! 

Think of it as a shot and just shoot it down and swallow it.