Painting is one of the easiest and cheapest ways to transform a space. All you have to do is pick a color, open the can, dunk in a brush and you’re good to go. Right? Wrong! The biggest mistake homeowners make when painting is not prepping the surface first. If it’s not cleaned, patched, sanded and primed beforehand, disappointing results are sure to follow. Primer, if you didn’t know, is the glue that helps paint stick to the wall. Without it, your carefully chosen paint color with look uneven and start to peel, sending you back to the store for another bucket and a second attempt.