I was surprised to see that TOH recommended painting the wall color first, THEN doing the trim.
One of the best time-saving tips I ever got was from a pro painter. He said to do ceiling, trim THEN walls.
You cut in the ceiling with about 1/4 - 3/8 overlap onto the walls. That way you don't have to be too fussy and can go fast. Then you roll the ceilings.
Next, you paint the trim, again allowing for a 1/4 - 3/8 overlap onto the walls. Instead of worrying about cutting in perfectly, you are moving fast and making sure you get a nice even coat on.
Finally, you cut in your wall color along the ceiling & along the trim. It is FAR easier to cut in the wall color along the trim & ceiling... you will get a nice straight line without the need for tape.
Plus, you are only cutting in ONE color, instead of cutting in the ceiling & the trim, which is awkward and difficult to get a nice finish.
This method really saves time when you are doing A LOT of painting. When we bought our old house, we had to paint every room before we moved in; this method saved days of time.