After you've decided on these aspects of the wood, you should consider the method by which the planks are joined together. This is particularly important if you're going to install the flooring yourself, as you'll need to be sure you're getting the right kind for the job.
Tongue and groove flooring consists of planks that fit together neatly with protruding 'tongues' fitting into corresponding grooves. It needs to be held in place using either nails or adhesives.
Click system is a newer method of laying flooring, and is designed to be easy to install without the need for nails, glue or anything else to hold the pieces together.