通常来说,是never do,比如:Never do things bad. 但若有分词作独立结构或有关上下文的其他场合,不能说never doing错,比如: I was never doing homework at home. 我以前从不在家做作业. We all expect never doing things bad. 我们都希望从善如流.
回答2:
10 Things You Should Never Do Before Exams - Exam Tips For Students