Clean the tube with alcohol if it is dirty/dusty before starting work
Do not make your own patches out of tube. Use the ones in in the Kit. I like the REMA kits and patches the best.
Use a rough sandpaper or emory cloth, the paper that comes with the kits is fine. They use to include a piece of perforated metal to roughen the tube, do not use this, it nver fully cleans the tube and usually fails. Do not clean or wipe the area after scuffing.
Use the included patch glue, not rubber cement from Lowes. Spread it larger than the patch you are using and let it dry until filmy/tacky. Place the patch on the glue then roll it out using something round from the center out pressing it down at the same time.
Before using in a tire talc the patched area so that it doesn't stick to the tire.

That's it. Anything else is not needed. Haven't had a patch fail yet.