In Writing

I can't emphasize this one enough. Get it in writing.
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Some people are going to say, "this is just an informal thing" or "I'm not a lawyer" or "what good will that do, a court would ignore it". All of those might be true. I am not a lawyer, I have never had to evict someone or go to lengths to enforce my housing agreement. But I think one of the reasons I haven't is because I have a written agreement. The biggest reason for having a written housing agreement is so you avoid getting into the position of having to enforce it. By putting it down in writing, it forces you to really think about what it is you are offering up for rent. It also helps ensure that your potential consumer does not have expectations you are not aware of. And finally, after the arrangement has been around for a while, it helps both sides remember exactly what they agreed to in those heady moments on move in day.
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The first thing to do is your homework. I don't know about every state, but here we have a renters rights book. I suspect other states have something similar. It describes the legalities surrounding Landlord tenant relationships. As the name implies, the rights established in statutes are more there to protect the tenant from abuse than the Landlord. For that very reason, as the landlord, you need to make sure you don't set yourself up for a fall in your housing agreement. The rules are going to vary from state to state and some large municipalities have their own rules thrown in there. Read the whole book and make sure you are in line with it.
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Instead of penalties, I think it is more important that your housing agreement describe what it is that your offering. It should assist you in running your household and your tenant by defining how they can stay in good graces. It should delineate the costs and when those amounts are due. How the utilities will be paid. Any special conditions you expect to be maintained. And actions that are not acceptable in the household.
Some things that I have in mine that I think are important:

• Items not allowed on the premises (appliances, Firearms, munitions, automotive parts or fluids)
• Actions not allowed on the premises (nothing illegal, Off road vehicles, quiet hours)
• Kitchen rules
• Storage outside the rented room
• How the utilities are paid for
• What day of the month the rent is due
• Visitor policies

All of this is aimed at being upfront when I interview a potential. That way, someone who can't abide by the rules doesn't move in. And that has been my general experience.
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For me, the biggest benefit of the written agreement is writing it forced me to think hard about what I was offering. I had to envision contingencies. And I have taken my experiences and expanded my agreement to make sure I don't repeat unpleasant experiences. It has helped me keep prospective and not over-commit myself.
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Back to the renter's rights book. There are also some details that may help you. In NH, rooming house is treated as a hotel and the proprietor can change the locks and send the tenant packing at anytime. In VT, if the room rent is payable weekly, the landlord only has to give 7 days notice instead of the normal 90 days for a typical apartment. There are rules about the ability to charge service fees, when the rent can be raised, etc. I say this not that I expect your housing agreement to be have draconian penalties, but instead because you don't want it to be in conflict with state law. This is the legal part.
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To wrap up, a written agreement is important so that both parties enter the arrangement fully understanding what their responsibilities are. It also provides a reference for the future so you don't have to rely on memory for your agreement. Your writeup needs to be legal, so read the renter's rights so you don't trip yourself.