LifeHacker.com has a great roundup of notetaking articles, many of which can be directly applied to using a tablet pc. So, whether you use OneNote, Journal, EverNote, or GoBinder to take notes on your Tablet PC / Ultra-Mobile PC, take a look at these tips. They are quite good.
In addition, give Tracy Hooten’s Hipster article a read. While not Tablet focused, it provides some good insight on where technology falls short, and the need for instant on / easy acces to electronic note taking in extremely portable devices. As I’ve written about before, I still use paperbased notebooks from time to time for many of the same reasons that Tracy describes.