What punctuation mark is used after a contraction?

You use the same punctuation marks after a contraction as you would after any other word.

For example:

* Period: She's going to the store.

* Comma: I'm not sure, but I think it's true.

* Question mark: Isn't that amazing?

* Exclamation point: That's awesome!

The contraction itself doesn't affect the punctuation choice.