• Consider that most of us have under lit rooms. To optimize lighting it's good to think about ambient light and task lighting. So you want to have an overall light that brightens the space and then 2 or 3 other areas that have more focused light (like bedside lamps or a lamp on the dresser) instead of just one overhead light. You could call this layering the lighting.
• The kind of light fixture you have makes a difference too. Check out this breakdown.
• Try a pink lightbulb and consider the wattage that you have going on. Too bright and you'll feel like you're in prison, too dim and you'll get a headache trying to read...
• Paint Color: cooler hues like blues, greens and whites tend to make the walls feel slightly further away (and thus a larger room) plus if the walls are a light hue, they'll bounce more light around, optimizing natural light during the day and lamps at night.
If you want a cozier feeling, warmer colors and wood will help to create a warmer atmosphere and darker colors on the walls will make them feel closer and more home-y.
• which brings us to: optimize natural light during the day by being able to keep your blinds open. If privacy is an issue, check out some of these ideas for privacy
What else should we add to the list?