Just go through the steps out loud, start with a really naive solution, say what's wrong with it, go on to the next. You can usually go through at least 3 level

Just go through the steps out loud, start with a really naive solution, say what's wrong with it, go on to the next. You can usually go through at least 3 levels of that. Also spend some time verifying the specification of the problem, ask about any potential edge cases. If you really know the problem well, go into maybe some extensions of it or harder versions.