The aperture is your first line of defense against overexposure, of which there are 3 main ways to adjust: dim your lights or wait for the sun to go away, use ND filters, and of course close down your aperture. We'll just focus on aperture for this quick tip!
The aperture is just like your eye, which opens and closes automatically for you when you enter different lighting situations. Many video cameras have an auto aperture which can be very useful for documentaries and instances where the light changes on you very rapidly. Though you should very rarely use it for anything narrative such as a feature film, because the audience can typically notice the change, and that's a bad thing. So more often you'll have it in manual mode, and you should know what it does to the image when you open or close the aperture.
When you open the aperture, it's referred to as using a lower F stop, or opening up the aperture. The numbers associated with F stops tell us how much light is entering the camera, each full F stop such as F5.6 to F8, tells us that twice as much light has either been added or subtracted.
The major side affect to increasing or decreasing the aperture is the resulting depth of field, or rather, how much of the image is in focus from the foreground to the background. When you let more light into the camera with a lower F stop, you're decreasing the DOF, which we typically see as a good thing because many associate that with cinematics/hollywood/etc.., though i warn you not to go overboard, too shallow a DOF can look silly, lock actors into a 1 inch space, and otherwise hurt your video instead of help it. I stick to a a DOF which has the background out of focus by just a bit so you can still make out elements in the background, but at the same time you wouldn't be able to read any text/signs, somewhere between the two sample shots i took of Ariel in the video are a good place to be.
You should also know that not all lenses that zoom have a constant max aperture, meaning that they might not have the same wide open F stop while zoomed as they do at full wide. More expensive lenses typically have constant max apertures, and less expensive lenses have variable max apertures. Exceptions of course do happen once in awhile.