I just want to point out that I'm really new, so I haven't even tried multiplayer yet. But I will say that I hold almost everything or use it in some way. Very rarely do I relax when messing around, and if I do, it's stuff that doesn't affect me so much, like wrists/neck/etc. So I would say that's a valid point.
All that aside, I noticed one tip missing, one that I have found extremely helpful in my short time here. That is to always think of how you would go about doing something in real life, and imitate that in your moves. If you're trying to figure out how to punch, for example, don't just pull your arm back and forward again, use your chest to get rotational power, and if applicable, yank back your other arm to add even more power. Stand up and do the move yourself, if possible. I mean, don't go find your cat to practice skeet or anything.
I also think this is important:
"You don't have to search the forum looking for high-damaging moves, they can tell you how to make your own!"
When I got my first glimpse of this game, my first thought was that it was an outlet for creativity. Every little battle you imagined as a kid could come to life here. Although that's slightly less that true, it still allows for endless personalization and individuality. That's very important to me. Make this game your own.