Legs are to be held straight and together while she opens up her legs around yours. It might be little more difficult to get the penis or dildo into the V, but then this gives a nice tight feeling.
Anal Reverse Cowgirl/Cowboy
"For penetration, it might be better to be facing away. (May not be as effective with eye contact, obviously.)"
"The bottom person's legs are in the air, presenting the butt to the sky (and partner). Movement and penetration are controlled by the top person, but there is adequate control over angle by the bottom person."
Anal Doggy Style
"The penetrate-ee (bottom) can have her back in an upright position (As if kneeling in prayer) or across (lying on all fours) or down (with the chest on the bed). This will allow for the bottom person to have some more control over depth and angle of penetration. The top person has a great view and a lot of control in execution."
In this position, which is a typical anal sex position where one person below straddles the penetrator and inserts the penis or dildo as if they were sitting on a fencepost. While the cowpoke is getting poked, there can be a better control over the angle and the movement. There is a much better eye contact in this position.
A pillow or two are positioned under your butt or under your lower back. This can help to tilt your pelvis up to match the natural angle of the penis or dildo. This is very much recommended for those who suffer from acute back pain.
"In this position hands-free vibration can add to the fun. The wearable We-Vibe (stimulating the clit and the G-spot and could be worn during intercourse) or a vibrating penis ring can provide the clit stimulation which is not fully available with missionary position."
Life On The Edge
"In this position, lie down on your back at the edge of the bed, and keep your thighs and legs dangling off. Bend your knees and put your feet on the ground. Your partner will stand or kneels between your legs and enters you. Your partner will have a great view and can control the deep thrust. You will kick back and have great enjoyment."
"In this position, you put your ankles high on your partner's shoulders. This will keep your butt lifted in the air. Your partner can hold your butt or your legs, and can simultaneously kiss and massage your feet. Your partner can totally control over the thrusting. However is not very great for stimulating the clit."
"In this position, both of you will assume a scissor shape, with your partner's leg between one of yours and the other outside it. Lots of pressure on your mons makes this position superior."