Well, my BEST advice is to hire someone to do it.

If you have the money, it's the best way, because they have all the equipment and deal with sanders and such every day, so they never get out of practice.
Other than that, sites like this one are helpful:
http://www.woodfloorsonline.com/techtalk/techline2.html . I've refinished a few floors in my time, and basically every time I just wished I'd spent the money on a contractor! All that sandpaper...all that dust!