If I had it to do over and had the bucks, I probably would have set up my 38-gal tank with a Fluorite (spelling?) substrate instead of gravel. It's much better for plants that get their nutrients through their roots. My plants are doing okay in a gravel substrate, probably because I add weekly doses of plant fertilizer (I was using Tetra's FloraPride, but I've switched to Flourish because everyone seems to like it so much). From what I've read, if you start with a Fluorite substrate you don't have to add liquid fertilizers at all. Additionally, the liquid fertilizers only help plants that take nutrients through their leaves.
So ... if setting up from scratch is an option, you might think about Fluorite for a substrate. (I wonder if it gets the water really cloudy when you add/move plants around, though.)
If you stick with gravel, just be sure to add fertilizers regularly. Also, have you got sufficient light? (I don't think it has to be as high as 2 watts per gallon, but anything over 1 watt per gallon would be nice.) And if your water's really high (or low) pH, be sure to select plants that do well in those parameters. I've found that most plants get along fine in a wide range of pH, but if you've got extremes, it can ... er ... "melt" some plants.
You will LOVE a planted tank. I'd never be without one. Have fun!
-- Pat