The most common use of up lighting is in a recessed cove around the top perimeter of a room. To maximize light output use a T5 fluorescent or LED light source that will wash the ceiling with light. This helps to create a brighter ceiling that bounces and reflects light throughout the space without glare. Combine this with lots of natural daylight to increase the overall light levels in a room.
Downlighting is just that: lighting that shines down to illuminate a space. Down lighting can sometimes be referred to as general lighting. Once it was simply the only light source in a room — that single fixture in the middle of the ceiling. If this is your only option placement and quantity of fixtures are the keys to attaining a balanced lighting level while reducing dark corners. Pot lights are also considered downlighting.
The light fixture should not be your only consideration — the type of lightbulb is equally important. Halogen compact fluorescent and LED bulbs come in a range of warm or cool hues. Much like the color of your walls the type of glow you want is mostly a personal decision. If your walls are covered in cooler tones you might want to warm them up with a lightbulb that casts a warm glow. Conversely you may want a cooler glow to brighten up a darker space.