Search the web there are neumerous good sites regarding the application of paint.
My tips I would say were to be surgically clean to avoid any contamination from oils etc.
Ensure you're correct distance from what you're painting.
Ensure it's not too cold ie a garage with no heating. You can always gently heat area to be painted with hairdryer and ( if using rattle cans) sit them in a bowl of hot water prior to to painting.
Lastly, practice, practice, practice....
Good luck
If you need more indepth info I can send you some links..