Keep a wet edge, and always paint from dry to wet. This will minimise brush strokes and roller marks. Don’t stretch your paint. You don’t want to glop the paint on, but scrimping will leave you with a patchy, blotchy paint job.
You will need the following tools to prep for a typical room: Spackle, putty knife, fine grit sandpaper, and a damp lint-free rag. You may also need paintable caulk and wood putty if you’re working on the trim.
Fill any holes or imperfections with spackle, wait for it to dry, and then lightly sand the patches. If you have a crack, you must first widen it slightly before spackling or the spackle will just sit on top.