For nice anal sex views we need to follow the following principles:
1) her belly, pelvis or bowl should be supported by steady and soft support not to hurt her if humping is strong -with an couch arm, pillow, bed corner or bar chair. For example if she is on her knees on the floor - you cannot hump her hard because all pushing force goes to her knees and it hurts.
2) basically it's doggy, in cow girl position however girls often get excited and they are fucking the cock themselves like assjob, for example Jessie Rogers in oily sex with Nomar.
3) if the girl is on her belly - put legs apart and bent in the knees, preferably the shoes should reach the floor. Please do not ask her put legs together and straight - looks too strict.
The best anal scene for me is Sabrinka's gangbang when her ass is fucked really hard on the couch arm. Also Henessy with Bruno X is good - on her belly on a lounge chair. Or a brunette girl in body stocking on her belly on the bed corner is asshole fever.
4) humping should be rough enough with a good amplitude