well we can't really give you actual techniques... but google is good for that (or so I heard) lol... I can say though that it took me a really long time to get used to it, when I started, at first I didn't want him to look at me, and then after a while I started to get more comfortable, and now I love it and Imma pro.
It's not really as complicated as you think so don't worry you're doing it wrong... its kinda hard to do it wrong lol... maybe ask him how he wants it and he'll tell you. Don't be nervous either. I really enjoy it because it makes my boy feel good... and thats my main reason for doing it. It can be pretty fun too, so don't stress. Also don't worry about your gag reflex so much. U don't have to try a superhuman feat if its difficult for you lol... just dont worry.