There are a number of things you'll need for this job before you get started:

1) First and foremost, protective plastic gloves and old clothes you don't mind ruining;
2) Wood Stain;
3) Stripping Agent;
4) Your choice of wood stain;
5) Sand Paper;
6) Putty Knife;
7) Steel Wool;
8) Buffing Paper;
9) Special squeegee for spreading the stain. Ask at your local hardware store if you're unsure;
10) Polyurethane;
11) D-natured Alcohol;
12) Aluminum pan;
13) Good mask or face cover.

Once you've gotten all your materials together, you can begin by removing all covers or carpeting. If the rug doesn't come up clean, you'll need to scrape it with a putty knife to get rid of the excess.

The floor doesn't have to look perfect, but it should be relatively clean. This includes getting rid of any tack stripping along the floor edges. This is most easily achieved by using a flat head screw driver to pull the tacking up.

After you've finished clearing the old materials and debris from the floor, use the stripper and spread it on an area of around three feet. It seems tedious, but you want to be able to clean the area quickly. Let it sit for five minutes.

Then pour the D-natured alcohol into the aluminum pan and clean the area you just treated with steel wool. As alcohol does evaporate, use it in small bits. Repeat the process from the beginning of stripping until you've covered the whole floor. Smooth any rough spots with sand paper and follow it up with a buffer.

When you've completed this process, apply the stain you chose to floor, allow it to dry completely, and apply two coats of polyurethane. Keep in mind that it will take up to a day and a half or two days for the polyurethane to dry.

The process can take anywhere from a week or longer, but if you work quickly, or with a partner, over several days, you can finish the project without a problem. This also depends how large the space is; if you're doing your house, expect quite awhile. If you're doing the dining room floor, expect significantly less.