Good light is incredibly important for live streaming. A lot of webcams will adjust their internal lighting options depending on the darkness of the room. In addition, if a room is too bright, the image can appear washed out and lack a lot of detail.
If your location has large windows that get a lot of sunlight, natural lighting will probably be enough. Your windows will need to be tall so the light doesn't shine only from above or below, because that can cause extreme shadows. You may want to augment natural light with the ceiling lights, lamps, or fluorescent lighting you have in your space.
When you have a space that's lacking decent lighting options, a useful and wise investment is a lighting kit. These kits include 2-3 different types of lights on tripods and can range from $50-$300. The best options are LED kits, since they allow for easy dimming and don't get very hot, like bulb lights.
Regardless of the lighting method you choose, there are a few things to keep in mind.
Choose a good angle. If your webcam is not parallel to your background, the image can appear crooked or unlevel. To ensure your webcam is at the proper level (both vertically and horizontally), try placing a mirror where you're going to stand and position your camera or webcam so the lens is directly in the view of the mirror.
Avoid extreme shadows. You can eliminate harsh lighting by adding more light to the location or changing how you're facing your light source and camera. If you're standing in front of a window, make sure that the camera isn't pointing in the direction of the window as well; this will make you appear in shadow. Instead, place the camera between you and the window.
Avoid overlighting. Too much light can make you and the space appear washed out and lacking detail. You can tone down a bright light by diffusing it. Place a see-through piece of fabric or paper over the light, or point it at another surface such as the wall or ceiling, rather than directly at your subject.
Ensure the colors are accurate. Your webcam may or may not have software that can change the hue and saturation of your image. If it does, make sure to use it to find the best colors that work for your space. If you're using natural light, you may need to adjust these settings at different times of the day. Testing will be required to ensure your colors remain consistent.