Color. Generally darker wood tones lend a more formal, traditional feel to any room, while lighter tones tend to be better suited for contemporary, country and casual styles. But since this is hardwood we're talking about, nothing is set in stone. So by all means, let your personal taste, preference, and style be your guide.
Location. Without a doubt, moisture is one of hardwood's most dreaded enemies. Which is why placing wood flooring in a full bath would be a bad idea - because of the heavy moisture content in the room. Likewise, you should avoid putting hardwood in any room that, elevation-wise, is lower than the level of your yard outside. Again, because moisture could become a big problem.
Type. Wood flooring generally comes as either strictly a solid wood or as a wood backing with a protective wood wear surface. Regardless of what type you select, another beauty of hard wood is that it can easily be resanded, recoated and refinished. Which makes it a perfectly recyclable flooring choice.