exposing ones dns on the internet

would anyone possibly enlighten me as it has been too long since i browsed ‘hacking revealed’…
would you talk to me about the kinds of things a security auditing tool would look for, if i had one, (hint hint) to probe my public servers. basic kitchen sink stuff most of interest but all ears to everything. i think you don’t need to be specific if you just help me get the idea. i would like more of a clue about exposing dns on the internet too if possible. have a great weekend and thanks in advance.