A large room will likely require all three of the basic types of lighting, as defined by the American Lighting Association: ambient, task and accent. The most important is ambient lighting, or general lighting that helps you to see and move about comfortably. Task lighting enhances specific activities, such as reading or cooking. Accent lighting serves to highlight pieces of art or decor, or certain textual or architectural features of the space.
The first step to attaining the right lighting for any large room is to assess all of the functions that the room will provide and determine which type of lighting they will require. Make note of social areas, like a dining table or sitting area, that will require good ambient lighting. If there is a television or viewing device in the room, you will likely want lighting that will be modifiable according to whether or not the TV is in use. Smaller task lights should be used to enhance individual activities, like reading or cooking. Once you've assessed your needs, take note of where and how many power sources you have. This will help you decide the type of lighting to install.
When considering ambient lighting, resist the temptation to simply install lots and lots of overhead lights, as it can look cluttered and reduce the openness of the room. Instead, consider track lighting, which covers a wide swath of space without being large and obtrusive, and generally only requires a single power source. Monorail or cable lighting systems are a bit more flexible than track lighting systems, allowing you to spread lights of different sizes or styles across an area in different configurations. Recessed lights, or even a traditional chandelier used with a dimmer, can also be added for social areas like a dining table or sitting area.
Task lighting should be planned in tandem with ambient lighting so that the two types of lighting complement, rather than conflict, with each other. In a large room, light task areas from more than one angle to minimize shadows created by ambient lighting. Task lighting is an opportunity to create intimate areas and use interesting design flourishes, such as an arc lamp over a sofa or a vintage library lamp on a desk in a corner study. If your large room contains a kitchen area, try pendant lighting to illuminate counter areas.
Accent lighting fixtures should remain subtle, so as not to take away from the pieces they are highlighting; however, the light itself should be stronger than the ambient lighting around it in order to engage the viewer. Wall sconces, down lights or spotlights can all accomplish this, depending upon the element of focus.