Here are a couple of threads that can help answer your question:http://www.hometalk.com/50182/refinishing-hardwood-floors-diy-or-hire-a-pro
Renting some floor sanding equipment is where to start.
The more aggressive machines require more skill and experience so you do not dig holes in your floor.
The milder machines are much more forgiving. They just take more time to get the work done.
I do the bulk of my work with a 17" orbital which is some where in the middle, I just started a project a couple of days ago.
If the floor is in decent shape and only has some finish dullness, then a screen and recoat is quick and easy. If the finish is worn through and you have leveling issues then a full sand will be needed...this too will vary widely.
Getting a floor flat and smooth is the ultimate goal and sometimes it requires a LOT of sanding.
Ginger, The common floor buffer/hardwood prep tool can be used to refinish hardwood floors. You equip an ordinary floor buffer with the proper attachment and quickly prep the wood flooring for refinish