Exposure lock is my favourite method to use when I have lots of time. It actually doesn’t require that much time to do, especially when you get in the habit.
If you have a subject that isn’t moving, such as a landscape scene, and you have time to be purposeful about what you are doing, this is the ultimate method for getting the perfect exposure.
I like to use exposure lock in combination with the “spot metering” exposure mode so that the camera will only take into account the light level at the exact spot in the frame that I tell it to. I decide what part of the image is most important for the exposure. For example, if I am making a silhouette image at twilight, I will point the camera at the sky and use the exposure lock button to exposure for the sky, then I recompose the image, focus, and take the shot.
To make this image of Battery Point Lighthouse in Crescent City, California, I pointed my camera at the bright red band of clouds in the sky, used my exposure lock, and then recomposed the image and pressed the shutter.
Check your camera manual to see how to use exposure lock. On my camera, I press a button with a * on the back of my camera.
Depending on the type of subject you are photographing and whether things in your scene are changing quickly or slowly, one of these methods will ensure you always get a good exposure.