do's and don'ts
Rules or customs concerning some activity, as in It's important to know the do's and don'ts of diplomatic receptions. This expression alludes to what one should and should not do or say. [c. 1900]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.