A big mistake many people make is in trying to keep wall colors “in their head” when they shop for new paint. Even experienced color consultants have difficulties doing this, so my advice is to gather some easy-to-carry items from the rooms you want to paint. It doesn’t need to be huge … maybe a few paint chips and fabric swatches attached to a piece of cardboard, a throw pillow, a color photo, or a box with samples of tile.
If you’re leaving the current paint color on the walls, don’t forget to take a sample of that paint with you by painting it on a sheet at least as big as notebook paper. The large amount of paint will help you visualize better when you’re at the store.