This is the most important step. Use the small square of sandpaper in your kit to roughen the area around the hole. This removes the slippery molding agents from the factory and gives the cement a textured surface to grip.
Here is everything you need to know about bicycle inner tube patches. The Two Types of Patches Bicycle Inner Tube Patches
Before putting the tube back in, run your fingers carefully along the inside of your tire. If the thorn, glass, or wire that caused the flat is still stuck in the tire, it will pop your newly patched tube instantly. When to Toss the Tube This is the most important step