I remember my choir teacher in high school told me, 'When in doubt, sing loud.' I'm a terrible singer, but I always auditioned for the musicals, and would get cast in them because I really would just put it all out there. That was really good advice, and I think it works for everything, not just acting.
Ethical decisions ensure that everyone's best interests are protected. When in doubt, don't.
When in doubt, make a fool of yourself. There is a microscopically thin line between being brilliantly creative and acting like the most gigantic idiot on earth. So what the hell, leap.
When in doubt, always opt for going naturel rather than hiding your skin under foundation and such. Line your eyes with kohl and mascara, put on some bright lip gloss and pinch your cheeks a little bit to get them all flushed and bright!
When in doubt, take more time.
I have a saying - 'You treat me good, I'll treat you better. You treat me bad, I'll treat you worse. And when in doubt, knock 'em out.'
When in doubt, punt!
When in doubt, throw it out.
When in doubt, wear a suit. Look at male politicians: you see them in a suit, and they look fine. But if you see a picture of them on the weekend or on vacation, there's a good chance they look terrible and unstylish.
Wise men, when in doubt whether to speak or to keep quiet, give themselves the benefit of the doubt, and remain silent.