First off, don't get any. If you are having a party, and you need to serve wine, for god's sake serve white wine. White wine is quite tasty, and much friendlier to carpets and tablecloths than red wine.
If the red wine stain is still wet, dump a lot of table salt upon the stain. The salt will absorb the wine, leaving you with a much more manageable stain.
Once that has been done, or if you have not had a chance to work on the stain for a day or two (recovering from a hangover perhaps?), you should use either tonic water or white wine on the stain. If the stain is on the carpet, don’t soak the carpet. You don’t want to be getting the matting wet. Don’t rub at the stain, instead blot it with a paper towel. Repeat this process until you’re not getting any more wine on the paper towel when you blot it dry.
Stain still not coming out? Time to pull out the big guns. Apply a 3% hydrogen peroxide solution to the stain, and let it stand for four hours. Come back and blot it, and apply more solution, this time letting it stand for a full 24h. Come back and blot it, and then let it air dry.
If that still doesn’t work, you might have to resort to some commercial products. The one that seems to be recommended the most is called Wine Away. You should be able to find it at a local shop that deals in wine accessories, any place that you can find home wine making kits should have it. If not, I recall having seen it in a few liquor stores, or you can order it online from various liquor accessory supply sites.