The correct way to hang a pool table light is a matter of opinion. There are unknowns to take in to account so we'll give you the basics. The main goal is to adequately light the entire surface of your table including the top of the rails and also allow enough room to shoot and maneuver under the light. With most fixtures the distance from the bottom of the lamp shade will be 36 to 42 inches above the playing surface. The length and width of your fixture and pool table will need to be taken into consideration. It helps to have a second person give you feedback on the effectiveness of the light while you raise and lower the light.
Most players agree that a fluorescent bulb whether a tube style or energy efficient bulbs provide the most even lighting across the playing surface.
The World Pool-Billiard Association (WPA) has a set of standardized rules for billiard lighting. This may be a bit of overkill but just in case you're planning a big tournament, here it is.
The bed and rails of the table must receive at least 520 lux (48 footcandles) of light at every point. A screen or reflector configuration is advised so that the center of the table does not receive noticeably more lighting than the rails and the corners of the table. If the light fixture above the table may be moved aside (referee), the minimum height of the fixture should be no lower than 40 inches [1.016 m] above the bed of the table. If the light fixture above the table is non-movable, the fixture should be no lower than 65 inches [1.65 m] above the bed of the table. The intensity of any directed light on the players at the table should not be blinding. Blinding light starts at 5000 lux (465 footcandles) direct view. The rest of the venue (bleachers, etc.) should receive at least 50 lux (5 footcandles) of light.