First of all, don't bother with FT Pro.
http://www.ridgenet.net/~jslayton/wilbur.htmlThis program is free, and I found it much easier to use than FT Pro.
Wilbur is the best program for randomly generating a heightmap for Earthlike planets. Its fractal noise features won't give you perfect plate tectonics, but "Hetero Terrain" is far superior to the stringy continents you get from FT Pro.
Now, I would like to note that I use GIMP, not photoshop. However, many of the features should still carry over.
If you're creating a rocky or icy planet without things like oceans and plate tectonics, you can still use Wilbur, but creating a SEAMLESS clouds or plasma texture in photoshop and desaturating it also works nicely.
If your planet doesn't have much geological activity and weathering, you'll also need craters.
Create a new, transparent layer, select a "fuzzy circle" brush, and randomly click around a bit. Set the brush to the size of your largest craters. You should now have a basic crater layer. Next, make a copy of the layer and run the "small tiles" filter (or its photoshop equivalent). Your second crater layer should have four 50% scale copies of the original crater layer, all tiled together. Repeat the tiling step 4-6 times, so you get craters on all scales.
Now, you need to merge your craters with the base heightmap. If you merge the layers at too high opacity, the heightmap will be completely overshadowed by the depth of the craters and not show up when we run the "emboss" filter later on. I recommend setting the opacity of the craters to around 25% before merging the layers. You might also want to play around with the blend modes: overlay and grain merge work well in GIMP.
Once you have your final height map, with or without craters, make a copy of the height map layer and run the "emboss" filter on it. This will make the texture look nice and three-dimensional. However, your depth should still be fairly low.
other stuff coming later...