Besides for finding the right person.
Most Helpful Guy
Use lots and lots and lots of lube. It's better to use too much than not enough. Spend ample time on foreplay. Communicate as much as possible.1
Most Helpful Girl
Get comfortable. If you're tense or uncomfortable with the person you're with, it's not going to be great. If you have to light scented candles and get massaged or you have to have a thorough discussion to alleviate your concerns, just do whatever you need to make sure both of you feel good.
Use a lot of lube. You might think you're wet enough to be okay but more never hurt. It can also make you more sensitive and makes stuff feel better so that's fun.
Foreplay is essential. If he can give you oral until you cum o cry before actually having sex then that would be great because 1. It's a good way of getting to know what you like and what your body reacts to, and 2. It helps relax your muscles which is important. If you rush foreplay, it'll hurt more.
And communication is vital. If you say stop, the other person stops, and you do the same for them. Talk through it, say if you're enjoying it and don't be afraid to say that you aren't cause all that means is you try something different that you'll probably like more.
Also have fun :P1