Style guides and usage books don't agree.
The Chicago Manual of Style and others recommend dos and don'ts.
The Associated Press and others recommend do's and don'ts.
Eats, Shoots & Leaves recommends do's and don't's.
What Should You Do? Unless your editor wishes otherwise, if you write books, spell it dos and don'ts; and if you write for newspapers, magazines, or the Web, spell it do's and don'ts. If you're writing for yourself, spell it any way you want. Just be consistent.
I was unsure, so I searched it before posting.
Then the AP and Eats, Shoots & Leaves are wrong because you never pluralize with an apostrophe. Never. I AM FANATICAL ABOUT THIS OKAY
lol