Artemis BJJ (MYGYM Bristol), Can Sönmez, Bristol, UK - 16/11/2016
Starting from the side ride, dig your near knee next to their hip. You're aiming to shove that as deep as you can behind their arm. Once it is in deep, flare the knee out towards you, which should make their arm available for your other heel to hook. Drag it back over your other leg and use your legs to lock that arm in place. At this point, you've already got a bunch of attacks available to you, but we want to get them face-up.
You'll probably be grabbing their wrist, their bicep, their sleeve or something else with your arm on the near side. With your other arm, reach under their far armpit and grab their shoulder. They could trap your elbow and try to roll you at this point, but that puts you where you want to be anyway. In the likely event they aren't foolish enough to do that, you have a few entries to the face-up crucifix available to you.
The one I prefer is from the Dave Jacobs seminar. Walk your feet back towards their bum, staying low and tight. Keep walking until you roll over their leg, putting them face-up. As you move into that position, make sure that your far arm is hooking back behind your head: otherwise, they can wriggle their arm free without too much trouble, enabling them to turn and escape. You can also begin to establish your grip mid-roll, reaching for the collar with your free arm.
You don't want their weight too far on top of you, as again that can help them escape: if that happens, shrimp your hips slightly to bring them down again. However, you don't want them to slip too far down to the mat, as there's another escape they can do in that situation. So, if they're too far down, scoop under them to prevent that escape.
You're now ready for the choke, which is nice and simple. With your free arm, reach around their neck and get a deep grip on their collar. Pull that around the neck as you would in a bow and arrow choke, getting additional leverage due to the way you've trapped their arm with your non-choking hand. For another boost of leverage, Aesopian's tip from Mastering the Crucifix is handy: bring their weight slightly onto you and bridge up into them.
Teaching Notes: Remember to mention grabbing your own head or the hand, also a few people were ending up a bit too far up or down. I'm not sure if I do a little jump at the the end, or just walk back. I teach it as just walking back and getting to a tipping point where they roll, but I should film myself doing this some time, to check I am actually doing what I'm saying. ;)