Just a quickie today. Marcin Borkowski (mbork) has a useful post on providing help in the minibuffer. It turns out that you can always type Ctrl+h when responding to a prompt in the minibuffer. If you have some code prompting for input using read-string you can specify what that help will be, either as a string or some other form based on context.
Take at look at mbork’s post for the details. If you’re taking input from the minibuffer it’s a good thing to know.