From the FAQ:
[1] Get on your side, facing your opponent. You do not want to be flat on your back.
[2] You must win the grip battle, and position your arms correctly. Best is if you can obtain an underhook with your far arm, and using your near hand as a "paw" to keep his other arm from hooking under your head or extending your near arm. Keep your elbows tight on your chest, acting as a barrier between you opponent and yourself.
[3] Do NOT allow your opponent to do one of three things: (a) underhook your far arm; (b) hook an arm under your head; (c) pull/push up on your near arm so that your near elbow is no longer serving as a barrier between your body and your opponent's body. If your opponent does any of these, you are basically screwed. If you are serious about escaping side control, you cannot let any of these happen, or your escapes are not likely to work.
[4] If you cannot get the underhook, then you will want to keep both of your arms folded on your chest, but placing the last third of your forearm, including the elbow, in (a) the armpit and (b) the hip of your opponent, so that both of your opponents arms are on the other side of your body, and your elbows are pressed up against his flank by your head. This is sometimes called "pin prevention posture." In order to get your far arm past your opponent's arms and under his armpit, try pushing on his elbow, as though you were trying to push him over you.
These first steps are CRUCIAL, and often not taught to beginners. If you lose the battle for positioning at the start, you are going to fail in your escape attempts.
[5] BRIDGE! Okay --- so your arms are in position. You are ready to escape. The first thing you must do is MAKE SPACE FOR YOUR HIPS. You do this by explosively bridging into your opponent. Make sure to bridge over one shoulder, towards your opponent, not straight up.
[6] Now SHRIMP your hips as far away as possible, rotating on your shoulder, using your arms to keep your opponent in place while your hips drive away. Repeat if necessary.
[7] At this point you will have your hands against your opponent, be on your side, and your hips will be far away. You have two choices here: Go to your knees or pull your near knee across his stomach, straighten out, and reestablish your guard. Work between them. If you insist on just doing one, you will not likely get it. Take what you can get.
That's it. Now, there are two additional "sweep" escapes that you can add after you master the basic shrimp escape dynamic --- sweeping your opponent over you (block his arm, grab a leg, and send him right over you), or driving into your opponent and flipping him over ("swim" your far arm into him as you switch base and drive). Both of these escapes require good timing, and for your opponent to be unbalanced. Even more important, both of these escapes require that your opponent be NEARLY PARALLEL to you, rather than perpendicular (as with normal side control). try to get your legs close to his legs, and distance your head/upper body, so that you are almost side by side. The "sweep" escapes will then become far easier. Usually these sweep escapes are good to do while your opponent is preoccupied with attacking (such as an Americana) or is busy trying to defeat a shrimping escape.
