White ceilings will look the highest -- darker or matching ceilings will look lower. Use special ceiling paint for the best results.
If you're looking to add the illusion of height, try a two color treatment on the walls with a darker color on the bottom and a light color on top. Make the transition between the two colors fairly low on the wall. With a white ceiling, anchoring the bottom of the wall with a darker color will make the ceiling seem higher.
Mirrors also help expand the space as does reducing clutter.