It can vary. Most often used is missionary variants. Positions from behind if contact with the cervix is desired. Spanking is fine, hair pulling fine, choking fine. Though I drawn the line at slapping/punching. Biting is good. Rope/restraints are good. Blindfolds. Whatever.
Currently I'm rather enjoying the liberator wedges I bought for the wife for Christmas.
"Well, then," the Cat went on, "you see a dog growls when it's angry, and wags its tail when it's pleased. Now I growl when I'm pleased, and wag my tail when I'm angry. Therefore I'm mad."