1. Lock the cats out.
2. Do yourself a favor and invest in the Benjamin Moore Aura low VOC (non-stinky) paint. I had to start with a coat of Kilz primer, which was brutally stinky, and then a coat of Aura, and it was like painting with heavy cream. Lovely. If you can't afford it right now, wait until you can. Worth every penny, especially when you consider it's truly one-coat coverage.
3. If I paint without a bandanna on my head, I get paint in my hair. If I wear a bandanna, I don't get any paint on my head at all.
4. Twelve years ago, I vowed never to paint behind a toilet again. Lesson learned? Never say never. I still hate painting behind the toilet.
5. Don't fool yourself: there is no painting just the walls of any room. As soon as you paint the walls, the paint on the woodwork looks dingy and shitty.
6. Lesson confirmed: the previous homeowners, aka Mr. and Mrs. Half-assed, did everything half-assedly. EVERYTHING. The wallboard is not tightly fitted, there's a gap around the window frame where he measured wrong and just left it, and the whole reason for this painting project is the half-assed wallpaper started falling off recently. Like, I brushed against it and a whole sheet came loose.