Begin by typing the obvious keywords into a text editor or word processor —
the ones you’ve already thought of, or, if you haven’t started yet, the ones that
immediately come to mind.
Talk to other friends and colleagues to see if they can come up with some
possible keywords. Ask them something like, “If you were looking for a site at
which you could find the latest scores for rodent races around the world,
what terms would you search for?”
After you’ve put together your initial list, go through it looking for more obvious
additions. Don’t spend too much time on this; all you’re doing here is creating
a preliminary list to run through a keyword tool, which will also figure
out some of these things for you.