Blowing help *ASAP*

Ok so my boyfriend thinks i give good blowjobs but i have giving them n everytime i see him he ask... im going to his house in a few hours and he really really wants one n has been asking for a while i keep saying no but i wanna this time. I just hate it tho . Can you guys give me tips on how to make me enjoy it and have a lil more fun then just gagging n tasting left over pee.