I have a whitewashed occasional table set that I would like to stain a dark color. In the essence of time, I am looking for the least lengthy process... Do I have to strip, sand, etc..? Can I lightly sand and add stain? Is there a quick method? HELP?

If it's the kind of whitewash I am thinking off, then just sand and stain. You will get a great effect if some of the whitewash is still left. Play with it first where it isn't noticeable.

In addition to the fine advise above, I would like to add that I have found much success in doing a light sanding and staining of furniture that is finished in a lighter color using a darker stain that is lacquer based.

I would add that going over the table with a product such as "benite" by daleys will ensure the stain absorbs evenly after sanding, otherwise if the table is made from a soft wood, you will get a blotchy look