This dictionary page lists many options for
現象, 跡象, and 表面 all seem like good candidates.
1) Which one is the most common one to use when translating
appearance in Mandarin?
2) Which one is the best for Cantonese?
3) Which one is the best for
Don't judge things by their appearance? 看事情不要看現象? This one seems common, but doesn't 現象 translate more into
phenomenon? Wouldn't 看事情不要看表面 be better?