My friend had been living in a rental lighting it most of the time by a single overhead light which explains why my apartment had felt so inviting and 'finished'. Most rentals are only equipped with a single ceiling light which absolutely kills a room's ambiance. Not only are they normally too dim to really light a room, having only one light source above you makes everything look flat and boring, not too mention how unflattering it is to the people sitting in the room.
If you only do one thing to spruce up a room in your house, consider the lighting. More than paint, more than a new couch, adding different light sources (i.e. lamps) to a room can dramatically improve it. And if you're thoughtful about it, you can even draw attention to the parts of the room you love and distract from the parts you're still working on.
Start with 3: Using 3 sources of light in one room is a good start. This might mean 2 table lamps on either side of the couch and a bubble lamp in the darker corner, or it might mean christmas lights on one wall, a table lamp on a desk and a brighter overhead light. Start experimenting with adding light to a room and see what feels best.
Check out some of our related posts on lighting:
How To: Replace Ugly Rental Ceiling Shades
Spruce up the Bedroom with Great Lighting
6 Chandeliers from Chandeliers.com
Grono Uplights for a Party
Pros and Cons of Recessed Lighting
Best Tealight Votives
Tablelamp in the Bathroom
[image SandersLauras Flickr]