Step 1: Getting it all together.
-a bicycle to paint
-some basic hand tools to disassemble the bicycle (wrenches, screw drivers, ect)
-sand paper (for removing rust and scuffing the old paint up)
-razor blade (helps when removing old decals, if present)
-a piece of stiff wire to hang the bicycle up with
-primer(about 2 cans for a large bike)
-paint of desired color(again about 2 cans for a large bike and also it is a good idea to use the same brand as the primer
-clear coat if desired
-and a clean place to work, with good ventelation and a fan
Step 2: Remove all the bits
For the most part you are interested in the frame, the handlebars and goosneck(the thing that connects the handlebars to the front fork), and the seat post, for painting. If you want you can also paint some of the smaller bits like the brake calipers, you well have to take them apart so you can just paint he arms.
This is also a good time to take stock of what needs replacing, like the brake cables and handle bar grips.