It is important to have a terms of use policy. This policy lays out how you want visitors to use your website.  Is their a certain age limit?  If your site is a blog, what kind of rules are you going to lay out.

I can give you some examples, no pornography allowed, no threats of violence toward other individuals and no foul language.  If any of these conditions exists, you will remove that kind of content from your site.   Also you will deny access to your website for people that continuously post objectionable material.

You need to lay out how you are going to deal with the issue of spam.  If for example, you see it in a post you will delete it.

I know I talked about blog type sites but for a regular website it is about visitors following procedures that you lay out.  I would suggest that you read other websites to get ideas.  I am not a lawyer.   I am saying with this document, a lawyer could be helpful.