One tech. I learned long ago is to get out of a grab from behind where you are lucky enough to have your arms free, and especially effective against a full-nelson. Essentially you just flail your elbows at his head, which should be right behind yours, but that's the tricky part. You have to get a major twist at the waist and hips (and FLING them elbows) to rotate with enough force to do any damage, otherwise you run the risk of making the person who is trying to hurt you madder than they already are. As far as wekaer vs. stronger there are a myriad of techniques, most of which would involve distractions and/or feints to allow you a split second advantage, whether enabling you to strike, get away, access a weapon, whatever. The main skill to have is recognizing that second and reacting in time.
John
P.S. Keep 'em coming Aslan!
Okay I completely forgot that I was going to second Aslan's theory about training ppl to get hit, with this short story. (Warning rant ahead)
I had a wake-up call a few years back when I was doing some friendly sparring with a guitar student of mine, who had also done some boxing. (I have had some boxing training) So when he asked if he sould use his "workout gloves" instead of the more padded versions we normally use (couldn't tell you the brand, but those foamy sparring gloves, not quite real boxing gloves)
Anyway, these gloves had only about 1-2 inches of padding on them, which I realized as soon as he landed his first punch. (About 10 seconds into it) Well, I noticed that it hurt, but we kept going. I am a few years more experinced than he, so I was able to keep him off of me for the most part, and still land plenty of punches, but when I hit him, it basically just knocked him around a little bit, while the few he was able to land, were growing more and more painful, especially as he started hitting spots he had already hit! Well, after about a round and a half my nose finally got knocked around enough to start dribbling, and we called it a day. Well in the time it took me to go inside and wash up, my face had revealed exactly how bad it was, with a huge mouse under my left eye, black eye (also on the left), slightly bloody nose, and a nice fat raspberry on my side where his glove had caught some skin. Fun fun!!! Since then we always use equally padded gear, and he has actually moved away.
But (the whole point was) I definently learned the value of being able to take a hit, and keep your head and do something about it. For about the first 20-30 seconds after he landed that first punch, I backed way off and went majorly defensive, trying to keep from being hit again. Well, I got hit anyway, so I switched to actively trying to hit him (alot), and making him worry about when to try to take a random swing in between me pounding on him. Well, thanks for reading my rant! Happy fistfights to everyone!

unch:
Also, I mentioned this elsewhere, but if anyone is in the Texas area and would be willing to get together for some training I would love to set it up, just contact me!