Look for single shoulders, in a medium grade. You don't need premium herman oak tooling leather, unless you plan to do some fancy carving. Avoid bellies, they are always wrinkled and mushy, shoulders are the most consistent thickness and firmness.
On cheaper leather, the grain is usually a little rough. The high priced stuff will have a nice buttery finish that almost has its own gloss while the cheaper stuff will look like someone got a little over zealous scraping the hair off, and it will be more of a flat finish. A little dye and some wax will make it look great though, or I really like the antique finishes that tandy carries(they still need a clear coat or paste wax to finish though).