Kata Gatame (shoulder hold)
The hold itself
He is on his back. You are on his right side. Slide your R hand, palm down under his head from the L, his R arm between your head and his. Join your L hand palm up with your R hand in the S grip. Your L elbow is out wide to the L, widening your base and preventing him from rolling you. Head is on the floor or your joined hands so he cannot extract his R arm. Your R hip is next to his R hip. Your hips and legs are facing away from him; if you are flat and he hooks your lower R leg with his L, he has control of your whole leg because bending your knee won't help you free it. If your knees face away from him and he hooks your leg, he only controls the lower leg and you can free it fairly easily by bending your knee and stretching your body out. Your L foot is posted out fairly wide.
Tightening the hold, getting the choke
Push him up on his L side about 45 degrees. Use your L hand on your R to manipulate your R bicep to make the gap smaller. Drop down, and stretch the L elbow and your body as far away from him to the L as possible. The hold should be much tighter now and you should be able to squeeze and drop the R shoulder to get the tap.
If you can't get the choke from kata gatame, move on to the head/arm choke.. Roll him up on his side the same way, tighten the hold with the R arm as before. Now take your L arm away, and then drive it back in hard, trying to touch your elbows together to make the hold as tight as possible. Face down. come up only slightly on your knees and drive "chest through the hole" for the tap.
Armlock counter to "telephone defence"
He may grab the back of his head with his R hand in "telephone defence", preventing you from closing the gap enough to get the tap. If he does this, let go of your R hand with your L hand. "Scratch his head" from the crown with the fingers of your L hand until you find his R wrist, then hook your L fingers around it and get a grip. Keep your head on the floor, tripod up and walk your feet around until you are approx. perpendicular to him. Drive your head forward with your legs, wedging your head between his R wrist and shoulder until your head is touching his. Walk back again SLOWLY, applying a lock on his R shoulder.
From side control, jumpover
You are on his R side in SC. Your L forearm is under his head, palm down. His L upper arm is next to your L ear. Put your head on the ground, and drive it up and to the L, so your L ear is on his L shoulder. Your spine bends so the top of your head faces the same direction as the top of his head. This puts a pre-stretch on your spine, so the when you do the jumpover, the pre-stretch will align you to be parallel to him. Come up on your toes and walk them in so your hips go up in the air; when there is no weight on your toes you can easily jumpover without getting caught in a guard. Join your hands in S grip and align your body in the correct kata gatame position on his L. Practice back and forth both ways.
From headlock control
If you are on his R side in side control, overhooking his R arm with your L, then switching your base to headlock is a bad idea; his R arm is already in place for him to get the body lock, and your body movement is almost perfect to set up the rolling escape for him.
Instead, UNDERHOOK his R arm with your L and lie on his bicep. Pull up with your L arm and try to hover, thus putting as much weight as possible on his arm. This will hopefully give him the idea that he can try to roll on his R side and take your back. As he tries this, you then have the opportunity to hook his head with your R arm and switch base. Bring your L knee high and make sure he has no gap to get his R hand through. Do not grab his hand as that will make him resist. If he pushes on your jaw with his R hand, push his elbow to your R with your L hand and drop down into kata gatame position on his R.
Push his R forearm to the floor with both hands as if going for an americana, but with his hand close to his head. Trying to lift your knees and feet off the floor as you push means ALL your bodyweight goes onto his arm. Hold his arm down with your L and slide your R arm under his head, grabbing his R wrist with your R hand. Now slide your L hand under his upper arm and grab your R wrist in a figure 4 position. Use the grip to lever his R elbow up and put your head on the mat next to his R shoulder. Release his arm and move to kata gatame on his R.
From front control
Your forearms are under his upper arms. Drive your L wrist in under his L armpit, twist it up and lay your chest on it for the "up and crush" to lift him up on his R side, as if setting up the top kimura. He may grab his arm or elbow because he knows the kimura is coming. If this happens, keep the up and crush, and walk your feet clockwise until your L hip is next to his. Now, back off enough for him to free his L arm; then drive your L shoulder under it and your head to the floor with your L ear next to his L shoulder, hook his head with your L arm and move to kata gatame on his L side.
Keep your L elbow on the L side of his torso so he can't roll you to his R. If you let it drift over to the R he can roll you.
From side/back control
You have side/back on his L. If he has a gi, use your L hand to pass his L lapel to your R hand under his arms. If no gi, just hold his R hip with your R hand. Your L arm goes under his L armpit and "snake bites" his R trapezius muscle from underneath. Push into him to create a reaction back; as he resists, use the push back to "disappear", rolling him over you until you are on your R side, Go slightly face down, enough to post on your R knee and head. Your grips prevent him turning away from you; encourage him to turn back toward you and as he does, move to kata gatame on his L side.
John wrote up how to do it as a counter to an escape from back control, but ran out of time before teaching it.
Using your weight
1. Hover - not so much "put your weight on him", but "get your weight off the floor".
2. Put your weight on a small area for maximum pressure.
3. Use your weight strategically, to get a reaction.
4. Find a way to pull up in the opposite direction at the same time.
You need to loosen up sometimes to allow the person to move the way you want. Shut off three sides of a room, but allow an easy, red carpet exit in the direction where you have the trap waiting.
In the old days, there was little information about MA. People got very good at a few basic techniques because there was nothing else to practise. Now there are thousands of techniques, and the temptation is always there to discard a technique after a few failed attempts and move on to the next. Work on the kata gatame submission before giving up and switching to the head/arm choke.