I know you want the positive, but can I dwell on the negative?
Things not to do, which I think would be universal unless you are told otherwise, as after all I guess we all have our own kinks!
Some men lean all their head weight on to the pelvic bone and then start bunting vigorously. This is really uncomfortable and any pleasure derived from the licking is taken away from the pain of the heavy head, which can also bruise. Please do not rest your head on any part of her body while doing this. It can hurt!
Biting! Please be very very careful if you are going to try to nibble, in fact probably best not to at all unless you are very expert and know what you are doing. Don't forget that you are not likely to be the only sexual experience for the lady you are with that day, which means she may be hyper sensitive or you may make her hyper sensitive for the rest of the day and if you do accidentally hurt her, then she can't work and she is not going to thank you for that. If in doubt, ask!
Don't carry on regardless! Some men don't listen to the ladies body at all and if she asks you to do something else, it is likely because what you are doing she is not enjoying. Take the hint and don't go back to bad habits if you are told something is not working. Other ladies may have told you they love it, but we are all different and that does not follow for the lady you are with.
Fingers! When you go for that shower, make sure your hands are properly washed, as lots of things can be hiding under your nails. If there is a nail brush there, use it!
Nails! Please, please, please make sure they are not too long and no jagged edges and clean. You can do a lot of damage if they are not and sometimes the damage shows up days later, so can not always be detected.
Tip with fingers, although not all the girls will want g-spot stimulation. Instead of putting your finger in straight and moving up and down, put a slight bend in your finger, so the tip acts as a pressure point against the wall of the vagina. Then instead of just going up and down add like a little royal wave to the motion. Start gentle and slowly build it up, but not too firm or you will hurt her. For me this often results in me gushing, but it can also result in the most glorious orgasm.
The technique should work universally, it it the pressure and how fast/deep you move your finger that will differ, as our bodies are not all the same on the inside and we have different levels of sensitivity.
One more thing about the tongue. Use it like a finger, use the muscles in your tongue so that there is some firmness to the touch (note firmness, not aggression) if the tongue is loose and limp, it doesn't really give much feeling and it does help if it wet down there, but not too wet, or that can feel weird.
Now I have my pet hates out he way I can open my legs with confidence! lol