References are too easily bullshitted. Unscrupulous people can easily get someone to pretend to be an old landlord or manager or professor over the phone. I believe conducting a criminal background check and a credit check (and charge them an application fee for the result) is really the best way to protect yourself. Of course, this cuts WAY down on your potential renters, since a lot of people looking to sublet are young with no credit, fairly broke and not willing to risk paying the application fee, or just have crappy credit. If they had good credit, they’d be renting from a property management company.
But find out how much notice you’re required to provide them, as well. Most of the time you can’t just barge into a lessee’s living space. You also can’t just pop in while they’re not home, barring an emergency (like a leaking toilet you’ve noticed is coming through the wall).
I think that fishbowls and outdoor smokers would be acceptable. You don’t want to make your potential renter pool nonexistent. And the more you have allowed in amenities/options, the more you can get away with charging. The fewer options you provide, the less you can get.
You should write in a clause detailing that they will need to provide you with at least month’s notice to move out, and that you will provide them with a month’s notice if you want them to move out.
You will also want to write in a clause that they’ll be required to allow you to show the apartment to prospective tenants during the last month of their tenancy (or beginning with the day that they provide you with move-out notice, whichever is earlier), as long as you provide them with x days of notice for viewings (2 days, usually). You can try to put in a subclause that they’re required to keep the place reasonably clean for viewings, although I don’t think that would be legally binding (more a gesture of goodwill that they may adhere to).
Keep receipts for your carpet. If a tenant causes damages requiring you to replace it, familiarize yourself with tenant law in your jurisdiction. Most places say that you can’t claim the full paid amount, you can only claim a depreciated amount based on how much time has passed. 7 years = full carpet depreciation in my jurisdiction.
Collect a deposit equal to one month’s rent. If you discover damages after someone moves out, repair them ASAP using the deposit, and mail them receipts detailing the amount of repairs and how that justifies you keeping it. You might want to get the carpet shampooed if it’s been a while, unless they shampooed it themselves, and you can usually get away with withholding a part of the deposit for this). If there are no significant damages, mail it back post-haste. Depending where you live, you can EASILY get fucked over in small claims court by holding onto a deposit one day too long.