You can either buy random plants or look for specific ones. Generally I have one or two that I want and then just pick whatever looks good for the rest. So far Amazon Swords have had the best luck, had some others that did ok for a while but I don't think I gave them enough attention. A. Swords are great for the back corners because they'll grow up nice and tall and will hide whatever equipment you have, they're also easy to take care of and fairly robust. If you want I can dig up some of the planted tank sites I used to use as reference, fire me off an email and I'll send you some links (have to find them first, not sure where they all are). Plants do make some more work, but not really all that much. Usually when you do water changes you can just take off any dead leaves so they don't clog things up or make the tank look unattractive. Proper lighting and some food are basically all you need, though you can always add a layer of something under your gravel to help supply nutrients too.
Here's what my tank looked like shortly after I first planted it quite a while back.
http://pictures.care2.com/view/2/313855707