Labels and punctuation.

Hello,

When writing labels, how do use punctuation? For example, The sign read 'Beware!'. Is that correct?

Or is it: The sign read Beware!. with 'Beware!' in italics. Also, The sign read 'Mandy's!'.

I am leaning to using italics because it looks cleaner.

Please advise.

Thank you.

Justin