I was sure I had written about this before, but can not find the post at the moment. However I “discovered” this handy trick a long time ago. If you have a digital camera or camera phone and can see what you last photographed and its a sunny enough day that you cast a shadow, you have a “free” Light meter. I know you camera probably already has a good one built in, that seldom fails, but hereif a nice way to check it is not being fooled by the light or malfunctioning. Alternatively you might just prefer to shot in Manual.
Just turn you back to the sun and point your camera down at yours shadow. it helps if there is some texture on the ground both in and outside the shadow. Take a picture and look at the texture. If the texture in the shadow is really hard to decipher you’ve under exposed. If The texture inside the shadow is fine but the part out in the sun is bleached out and hard to decipher your over exposed. When the detail can easily be seen in both the shadows area and sun-lit areas you will have the correct exposure and anything you photograph in the foreground of a photo will be well exposed. Providing you are not looking straight into the sun or have you camera angled up above the horizon (ie you have mostly sky)
So what to do?
Underexposed (left hand photo) needs more light on your subject so you could use the aperture ring (if you have one) to add one extra stop of light. This will double the light being sent to the sensor. The traditional f-stops are however not linear (for example f11 to f8 is considered one stop). Alternatively you can use The EV (Exposure Value) setting that most digital cameras and even smart phone camera apps now include. These normally are indicated by a small square with a diagonal split and + and – against dark and light shades. In the case of the underexposed you want to add to the EV value either select +1 EV or move the EV slider to the right (a higher positive value). The final option is you can change the shutter speed, let it stay open for longer. This is a bit easier to remember since changing from a speed of 1/120th second to 1/60th will double the light reaching the sensor during the exposure.
Overexposed (right hand photo) is just the reverse you need less light during the exposure, Shutting down the aperture (moving to a higher f-stop number) or using a negative Ev (eg –1 EV) or taking a faster shutter speed.
On a sunny day the reflections on a LCD screen can make it very hard to read, for example judging colour and tone. So this is why it is a good idea to include some strong texture. Even though there may be a strong reflection on the screen you should be able to still make out the relative texture in the shadow or sunny parts of your image.