The document that prevents disputes.
WHY YOU NEED ONE
Without stated terms, every disagreement is your word against theirs.
WHAT TO COVER
What the service includes What it does not Payment terms and what happens on non-payment Suspension and termination process Backup arrangements, explicitly
Acceptable use: what content and activity is not permitted
Resource limits and what happens when exceeded Support hours and response expectations What happens to data when the account ends Who owns the domain
THE BACKUP CLAUSE
State plainly whether you provide backups, how often, how long they are kept, and whether restores cost anything.
This is the single most disputed point in hosting, always at the worst moment.
ACCEPTABLE USE
Prohibit spam, malware, phishing and illegal content explicitly.
You need the ability to suspend an account causing harm, and that requires having said you would.
KEEP IT READABLE
Plain language, with headings. Terms nobody can read protect nobody in practice.
WHERE TO PUT THEM
Linked from your site, and referenced at signup.
GETTING ADVICE
For anything significant, take proper legal advice.