Good lighting is all about control and how you have controlled the light in any situation to create the look you are after. Control of light can be achieved with some of the following techniques; flagging, bouncing, dimming, netting, diffusing and colour correcting.
The following video links will take you to chapters of a Lynda.com course which explains how to set up lighting effectively.
Flagging
Blocking the light so it does not spill over, creating a barrier using a piece of fabric in a frame or a piece of card.
Bouncing
Bouncing light will generally give you a softer, shadowless light.
It is also a good technique if you are not able to place a light where you need due to space/position restrictions.
Dimming
Adjusting the voltage supplied to a light which then lowers the intensity of the light output
Netting
Using nets, scrims or gels placed in front of the light beam reduces the light intensity
Diffusing
Making the light softer by spreading it over a broader surface.
Colour Correcting
Might be needed when working in different environments with different colour temperatures (e.g. indoors, daylight). Colour temperature can be adjusted on most LED lights, but may need to use correction gels for older style lights.