I was recommended from many guys when to use the lens hood.
Well, here are some basics:
- anytime outdoors, even if you think you don't need or you think you're not shooting direct into the sun. So put the hood on outdoors, it helps with the photos not looking slightly discoloured.
- when you're using flash and you know there's some objects in the sorrounding reflecting light.
- when you are shooting amongst many people with flashes on.
and if you haven't already (because I know some people don't), put the hood onto the lens the other way round so in case you need it you won't need to dig it out of your bag or you've left it at home.