Use the Right Equipment
A belt sander or palm sander won't cut it for this job, so it's necessary to rent special equipment from an equipment rental store or a home improvement store. Necessary equipment includes a drum sander (or equivalent heavy orbital sander or box sander), an edger, and the corresponding paper in different grits. Don't be shy about asking questions and have the person renting the equipment demonstrate how to use the equipment before leaving the store, including putting on and taking off the sandpaper.
Always get extra sandpaper, as its often takes more and the rental place will buy back any unused paper. Don't forget plastic sheeting to seal off areas of the house from dust and tack cloth to clean up dust when sanding is completed.
Have a Plan
There's plenty of great step-by-step information for free on the Internet about the actual process of sanding your floors, as far as the actual mechanics. Start in a low-traffic, low visibility area to get a feel for it, and where a few small mistakes won't be too glaring. Know what rooms to complete in what order before starting.
Sand everything down with the roughest grit then move up to the next grit; resist the urge to get one room done completely, then move on to another room, etc. If sanding a lot of floor (more than 500 sq. ft.), be prepared for it to take 2-3 days to complete just the sanding. Allow time for the stain and polyurethane to dry between coats, as well as 2-3 days after applying the final polyurethane coat before any foot traffic.
https://suite.io/seth-shafer/311k2vx
http://www.youtube.com/watch?v=pv9lAt_i8kg
