So, I just attended a seminar about self-help skills last Thursday. It was put on by an OT who went on a tangent to explain some things about kids with sensory issues. I'll try to summarize it, because it was pretty good.
Basically, all kids can get overstimulated. Our kids can get overstimulated more easily than others. Kids can also be in need of stimulation and seek it out. In between those two states is kind of a happy place where they will be calm and receptive to learning, eating dinner, etc.
You can help your kid get to that happy place by providing the right kind of sensory input. Repetitive linear motion (bouncing, rocking in a chair, seesawing, and swinging) can calm them down. Lifting heavy things (pushing a wheelbarrow around) is another good way.
Want to get them perked up a little? Pick'em up and twirl them around.
Chewing gum or eating chewy foods can be calming, whereas crunchy potato chips may have the opposite effect.
That's the quick and dirty version. Here's a link to more info.
We try to keep chewy tubes around. You can clip them to a belt loop and provide an alternative to chewing on a shirtsleeve.