*what you will need, a tire plug kit from any auto part store. I believe they have motorcycle specific repair kits but it exactly the same as the ones for car tires.
1. Never attempt to plug a sidewall! Your tire's sidewall is under different strains and pressures than the part that makes contact with the road. Plugging a sidewall can result in a blowout, so don't try it.
2. Spin the tire until you find the evil little metal bit that made a certain hour of your life really unpleasant.
3. In your tire plug kit, you'll see a tool that looks like a round file with a handle. This is used to clean out and rough up the hole in your tire prior to plugging. Go ahead and remove the nail or screw from the tire. You might have to grip the nail with pliers or Vise Grips if it proves hard to remove. If it's a screw, you can just unscrew it. Take this tool and ram it into the hole. Move it up and down a few times to roughen up the inside. You don't have to go nuts on it, a few solid pumps should do it. Once you think you've roughed it up enough leave it in the hole.
5. Now you finally get to play with those cute little tar-worms (the not so clean way to repair tires, but it works). Peel one of them off and thread it through the tool that has an eye on one end, like a giant needle. You'll have to pinch the end of the worm to get it in there, but it can be done. Pull it through until it is centered in the plugging tool.
6. With the worm threaded onto the plugging tool cover it with the rubber cement or whatever adhesive that is included in your kit.(you can be pretty liberal with the cement)
7. Remove the file and quickly stick the end of the needle tool into the hole in your tire. Once it's in just a little, start to really push on it so that the tool and the plug sink into the hole. It will be pretty hard to push in, but you're looking for a tight fit to hold in all that air. Push the plug in until only about 1/2 inch is sticking out. Now pull the plugging tool straight out, leaving the plug where it's supposed to be, in the hole.
If you have something to cut the ends of the plug off with, go ahead and trim it close to the tire. If nothing's handy, you can trim it later.
6. Now fill your tire with air to the proper tire pressure and you are 100 percent back in action. Well done, you can now repair tires!
This is a picture after riding a few hundred miles without incident.
Now let the argument begin on whether or not it is safe to ride a plugged tire for longer than it takes for you to get to safety.
DIY by Matt Wright from About.com and yours truly.