There's no way to say exactly what can get your account suspended across every host, but there are some things that you can do that will cause most providers to suspend your account.
The most common reasons for account suspension are:
• exceeding your storage and bandwidth limits
• frequently using up lots of server resources (i.e. CPU and memory)
Other causes for suspension are listed include:
• Spam email messages being sent from your account
• Hosting or linking to material that infringes the rights of a third party or any Federal, State, or local laws
• Hosting or linking to pornography, especially child pornography
Sometimes a host will give you a warning before your account is suspended, but not always.
There are usually few causes for an outright account termination, but two examples of possible grounds for termination are:
• attempting to gain unauthorized access to another customer's account or files
• verbally or physically abusing or threatening the company's employees
For specifics, you'll need to ask your hosting provider's abuse, legal, or support department or check their Acceptable Use Policy, Terms of Service, and other legal agreements.