Mend a puncture

Get a bike. Puncture it with a nail.

Done that? Excellent!

Now buy a puncture kit at the closest supermarket. Take your punctured wheel out of the bike and separate the inner tube from the rim.

When you've done that, fill the inner tube up with air and put it inside a bucket of water, this will help you locate the puncture (look for the bubbles). As soon as you've found it circle it with some chalk so you don't loose the spot. Rub the spot with some sandpaper to wear out the edges that are sticking out.
If you don't, there will be a space under the patch and it'll come off.

Now stick a blob of glue over the punctured are, spread it with your finger and wait for about 10 minutes. Stick the patch on the exact place where you've spread the glue, press the patch against the glue for five minutes so it sticks properly.

If you had the patience to do all that, you're nearly finished. All that's left now is put the tube back inside the wheel, jam it into place and pump it up again.

This is a nice easy way of writing two hundred words without thinking a lot. In fact I was just going through the steps because as it happens I've got to mend my own bike right now.