I use two rules:
- If I shot in .jpg (family, holidays, not creative pictures..) I let the camera exposimeter do its job. I only over/underexpose a little when necessary. For example, if I take a picture of a snowed lanscape it is necessary to overexpose to have the snow white.
-If shot in .RAW I have the following procedure (in manual mode):
1) Choose the desired f-number.
2) Use the spot measurement of light and measure the brighest light in the picture.
3) While pointing to the brighest point adjust shutter speed until the measurement is in the top right (+3EV).
4) Recompose the image and shot.
With this procedure the brighest lights of the picture will "fall" in the right top of the hystogram but without being burned. So, you will not lose information in the high lights.
Even if the picture is not very contrasted it is a good method because although you will see the picture very clear, the lights are full of information. You will have time later to reduce the luminosity in PS. By the opposite, if you expose for the medium tones you will burn the high light (without possibility of recovering!) and you will have a lot of noise in the shadows.
English is not my usual language. I expect o be more or less understood.
Sorry for the mistakes