Best Hangover Remedy
The very first thing you need to do in this situation is get yourself out of bed and into the shower. Chances are your hair smells like smoke from whatever bar or club you were in, and the stench is probably nauseating. Next brush your teeth, you know you didn't do that before you passed out last night.
Next, see if you can keep any fluids down. If you only have water that's ok, but Gatorade is better, I highly recommend keeping a stash handy for situations like these. You want to avoid orange juice (too acidic) or anything else that could upset your stomach.
No matter what you decide to drink the most important thing to remember is to SIP whatever you're drinking slowly. There's no question that you're super dehydrated, but chugging anything will surely end with you puking your guts out. And don't think that puking is going to make you feel better; instead it will further mess up your electrolytes.
I would then recommend finding an ice pack or bag of frozen veggies (peas work best because they form to your head the best) stick it on your forehead and relax for ten minutes. During this time you can also try eating a little bit of something very bland, such as a bagel, toast, or the pizza from last night that arrived after you passed out (just kidding).
If you're going to take some sort of pain reliever for your headache, make sure that you eat something with it because if you don't it will only upset your stomach more. I recommend taking ibuprofen, such as Advil, because it relieves the pain and also stops inflammation.
At this point in time depending on how you feel I would recommend doing some sort of light activity. This can range from taking a walk, to going for a run. Just don't do anything for longer than 30 minutes, the point is to get your metabolism going so it can push the toxins out of your body, not make you feel even worse.
If you live in an area where you have access to the ocean I highly recommend going for a swim. The water pressure will help the lymphatic system drain, and increase your circulation (therefore eliminating toxins from your body).
I would then take another shower, drink some more water or Gatorade, and get back into bed for the next 1-3 hours. Clearly, your body was put through the ringer last night and it needs significant rest to repair the damage you did.
When you wake up you should feel a lot better, maybe well enough to eat a more substantial meal. Or, maybe you feel so good that you're ready to do it all over again? Some people never learn.