A couple of things I picked up from talking with Rodrigo after class on Thursday.
(1) It's all about movement of the body. The reason my arms and shoulders are so sore is because my upper body is doing all the work.
(2) Change the angles. If the guy in your guard is working you hard to your left, then you might be able to sweep him in that direction. Jiu jitsu is just judo on the ground.
(3) From Cindy: When under sidemount or half-guard, never waste your time or energy by hugging the guy on top of you. Always work to get your arms/hands between your body and his.
Also, "ass out" or hip escape when trying to fight off a sidemount or half guard pass. Joachim Hansen has that great reversal move where he hip escapes, then throws a leg over the back of the top guy. In one variation, you throw the leg up toward the head and use that momentum to drive you over. In the other variation, you throw the leg up toward the upper chest and use that momentum to drive you over into rear mount.
Cesar Gracie's tips on hand control are working wonderfully. Not only does closing the collar make it easier to control the guy's body when you are in his guard. But it also helps keep your elbow in. I've got more work to do, but I feel more confident about being in the guard because I'm finally getting what Cesar meant.
Also starting to do a lot better at automatically standing up to pass the guard. I want to be almost known for that. I'll still keep trying to work Saulo Ribeiro's on-the-ground pass for variation. But I'm fighting for upright position every time now.
(3) When in the "passing the knee" stage of passing the guard, underhook the body on the side opposite the one you are trying to pass. Keep your hips low and try to bring the opposite knee/hip over first, if you can. Also, try and overhook and pin the arm on the side you are passing to. It will help keep the guy from blocking your knee with his hand.