And from the "Design Methods" chapter of the soon-to-be-published-if-formatting-it-doesn't-kill-me-first Alice Through the Proscenium:
Comparables - A kind of go-by… Look for solutions to parallel problems. Say your solution must do two things at once; well, what other designs do that? A toaster toasts two sides at once. A pencil can draw and erase, it’s built-in. Some unrelated design may hand you a clue to your problem.
Talk – Kick ideas around with the director, other designers, or friends. With the right company you find yourself designing (and laughing) until quite giddy. Nothing is more fun than a design party! Sadly it’s also rare, because finding someone with the required quick wit, joy de vivre, and lack of ego is tough. You must respect your sparring partner (and vice versa). Treasure those you find.
Otherwise, be cautious. Directors may take your unconsidered comments or first ugly scrawls seriously. Try not to frighten them; you artists are notoriously weird and dangerous people.