Purchase tester containers of the shades for your potential paint colors. Most paint stores only offer testers in one finish, usually eggshell or satin, which is appropriate for most wall surfaces.
Paint a sheet of paper or foam board with each paint color. Allow the paint to dry.
Tape the sheet of paper to the wall in the room you plan to paint. If the walls are already painted, place a sheet of white paper behind the painted sample to get an accurate assessment of how the color looks on the wall.
Assess the paint sample throughout the day to see how it looks in various types of light. Move the sample around the room to see how it looks against furniture and flooring, in dark corners and next to the windows.
Paint additional sheets of paper to test coordinating trim colors against the wall color. Try different combinations until you find the one that works for the room.