An average fellow
The best sex positions are fair game—so experiment! Sex expert Emily Morse of SexWithEmily.com suggests the Crouching Dragon: Wrap her arms around your shoulders and her legs around your midsection before you crouch down in a squat so that your body makes a human chair for you. Press her body closely up against yours as you grind.
Spend 10 to 15 minutes in foreplay to help the vagina expand, and use lube. Choose her-on-top moves to control how deep you go. Have her lean over your body with her hands on either side of your head on the floor or a mattress, “as if you’re about to do a pushup,” says Morse. “It also helps for you to bend your knees so you can lean back for support.”
Smaller than six inches
Go rear-entry, says Debby Herbenick, Ph.D., a sex researcher at Indiana University. This offers you deeper penetration. Rest her head and shoulders on a pillow, lift her butt up, then have her squeeze her thighs. The tighter her legs, the snugger the fit. (Avoid lube: With a smaller guy, friction is your friend)
If you have a slight sideways shape, “stand next to the mattress while she lies on it,” says Morse. “Alternate angling her to one side, then the other, almost curled in a ball. It is useful sexual tips. You can use your shoulders for support while you thrusts and find which of the positions feels best for her, depending on which direction your penis bends.”