If you do a google search for "trekking poles + technique" or something similar, you should get a lot of good articles. Here are a few.
http://www.personal.dundee.ac.uk/~pjclinch/poles.htmhttp://www.backpacking.net/trekpole.htmlI'm no expert, but I have used them a while and have learned a few things. Probably the most important thing you want to learn, is how to properly use the strap on the pole. Most people i see using these poles aren't holding them correctly. If you thread your hand from under the strap, and then grip the pole so the strap runs under your palm (hard to describe, but easy to do) then all the weight will be supported by your wrist and the strap. This way, you actually don't have to hold on to the grip at all, the only time you need to actually grip the pole is to lift it off the ground to swing if forward, not to support your weight. Doing it this way, your hands won't cramp up, your palms won't get sweaty, and you won't have to worry about blisters.
I started out with just using one pole to try it out, but I would recommend getting two poles from the beginning, because you really don't get as much of a benefit from just one pole. I bought some cheap $20 ones from Target (Walmart carries them for $10 each now), I figured if I like them I'd upgrade to Leki's or something better. But after about 5 years of using the same ones, I've never really felt the need to upgrade to anything better. If you're using them right, all the fancy cork grips and anti-shock tips don't really seem necessary, although I still want a pair of carbon fiber poles just for the weight savings.
Once you start using them, you'll probably find your own style. I just do whatever feels comfortable, and it seems to work. I know I've avoided a at least a few serious sprains or torn ligaments with these things, especially when hiking with a heavy pack. Plus they work great when crossing streams or logs, it's just like having another set of legs. about the only other thing I would recommend is don't be afraid to adjust them frequently, it only takes a few moments, but having the right height helps a lot. And you don't have to adjust them equally either, if you're walking along a slope, make the downhill one longer and the uphill shorter. If you want more info just PM me.