I've recently finished painting the majority of the interior of my house: upstairs hallway, stairwell, living room, dining room, kitchen, stairwell, downstairs hallway, downstairs bathroom, and family room. It has taken me about a week and a half. And I've learned a few things ... (skip if you have no desire to ever repaint anything).
1. Paint Quality Counts -- before this, I'd always bought the cheapest paint to do the job. This time I researched on Consumer Reports and bought the Behr Premium Plus they recommended. It was great paint! Excellent coverage, beautiful, rich color, lower odor than I remember from other paints. It was a bit thicker than I was used to, but it worked beautifully!
2. Do the Math -- measure your rooms, subtract out windows, doors, archways to calculate your square footage. Look at your paint's expected coverage, divide, etc. Then, I always buy an extra gallon, just in case.
3. Prep Matters -- lay down plastic drop cloths over your furniture (I cover furniture, but not my floors), mask with painters tape, edge with an edger or brush then your rolling will be fast and easy and done. When you remove switchplates and outlet covers, stack them on your counter, but just rescrew the screws back into their holes, sans cover. You'll never lose another screw. If you intend to hang arkwork back in the same spot, it's probably better not to spackle and sand the holes, just paint over them. Even if you seal the hole with a tiny coat of paint, you'll likely still see the mark and the nail will slide right back in.
4. Take Your Time -- I did one room/section per day and allowed it to dry overnight before moving on. I could rest my arms and shoulders that way and make sure I'd adequate coverage before starting a new area.
5. Painter's Tape is Your Friend -- mask everywhere you can. Even if you have the steady hands of a neurosurgeon, you will eventually blob some sort of color where it doesn't belong, and if you've pre-taped, you should be all right.
6. Remove Tape Quickly -- as soon as you've finished working the room, while the paint is still wet, remove the painter's tape. If you wait until the paint dries, you will have created a gorgeous latex seal between your wall and your tape, requiring an X-acto knife for removal (lest you peel the tape and part of the paint comes along with it).
7. Lighting is Key -- Work in whatever time of day brings the best daylight into the room you're painting. Daylight will cast fewer shadows than houselights (unless you're using contractor's floodlights or something) and will give you a better indication of whether yo've missed any spots or if the old color is showing through your new topcoat.
8. Don't Kid Yourself -- If you can see hints of the old color through "here and there" and think your guests won't notice or that you'll get used to it ... don't kid yourself. You need a second coat. And follow the manufaturer's instructions for the second coat, or your new paint will peel the old paint off the wall in a haphazard and skin-peeling-after-a-bad-sunburn sort of way.
9. Clean Up Right Away -- I know you're feeling grimy and your clothes have paint smudges on them and there's probably paint in your hair ... but clean your materials before you shower. Not only are you still messy, so you won't mind as much getting your fingers in those edger crevices and gouging the paint out, but everything will be easier to clean while it's very fresh.
10. Some Things Shouldn't Be Cleaned -- Planning to do more painting with the same color tomorrow? Just wrap your roller tightly in plastic wrap and it will be good to go again and again until you are done with that color.
11. It's a Messy Job -- Wear old clothes. Use your fingers to scrape drips off your trim (if you haven't masked it) and then wipe your fingers on your jeans. Climb down behind your toilet and paint wrong-handed while tilting your head sideway to see under and behind the tank (I speak from experience).
12. Be Proud -- line up your used gallons of paint, to remind yourself of how far you've come. Tell everyone (repeatedly) that you're painting your house on your own. Revel in your new color ... go out and buy throw pillows, curtains, etc. to match.
I'm sure there are more things that occured to me while I worked, but I think that's the nitty-gritty of it. Next sunny day I plan to take "After" pics of the house and will share them soon.