Avoid asking users to memorize stuff. People will have a much easier time recognizing an option if they see it rather than recalling it from memory.
Speaking of the autocomplete example above: of course we have to start with a recalled search term first – but this might be sometimes only be a vague base of what it is that we think we are looking for – but as we type it we can see other suggestions. This might help us fill the form out because we have recognized the term we were looking for.