Found someone to install new hardwood floors in the bedrooms, but planning to purchase the wood myself. Any general advice? Avoid Home Depot? Worth paying a little extra on any features?
A few thoughts for you. You didn't provide a lot of detail about the specific situation you are going to have the floors installed, so some of the following may not be applicable in your situation.
Do you have a particular wood species in mind?
Decide which way you want the boards to run. Some people like the boards to run in the same direction as light from windows. Others like the boards to run the longer dimension of the room. Once you have the boards, you can lay some down and see which direction looks better in your situation. This can be forced by the type of subfloor you have, and/or the direction of the floor joists.
Get the wood far enough in advance of the install to let it sit in the room where it is to be installed. Most places recommend at least four days. This allows the wood to acclimate to the temperature and humidity of the room. I try for at least a week. A nuisance yes, but I'd rather deal with that than flooring that isn't fully acclimated.
Check with the installer to see if he has any preferred suppliers/discounts.
No reason to skip any of the big box stores. They may be carrying stuff from the same manufacturers as the "flooring stores."
Make sure the product is correct for your installation situation. If you are installing in slab on grade rooms as opposed to second story or above a basement, regular tongue and groove hardwood boards will not do well. You will need "engineered wood" flooring.
Make sure your subfloor is sound, solid, level (or at least flat) and doesn't squeak before board one of the new finish floor is installed. Check it and put in nails or screws anywhere it feels a little bit soft, loose or squeaky. Make sure there are no lumps, bumps, rises or low spots in the subfloor. They can lead to the hardwood squeaking.
(If applicable) See what the extra thickness of the hardwood floor will do to the height of the top step. You may not think an extra 5/8 or 3/4 inch (assuming tongue and groove hardwood boards) is much, but it can make ascending the stairs difficult, particularly in the dark. You will catch your foot on the top step much more often than you think you will.
I would go prefinished. You haven't seen dust until you have hardwood floors sanded and finished in place after installation. Biggest reasons not too are to get a particular floor color or to have improved water resistance by finishing in place.
Depending on what you get for your finish, you might want to investigate adding a coat (or several) of polyurethane or other clear coat over top. It will extend the life of the finish by a lot. It will also improve the resistance to spilled liquids by filling and sealing the tiny spaces between the boards. Some factory finishes don't need it, or can only accept specific ones, or none aat all. Check what you decide to get. Dad did the overcoat on the hardwoods when we were growing up. Four kids, lots of friends, two dogs, and six cats. 20 years later, the stairs were the only thing that showed much wear.