The rental application must be completely filled out. That means no blank spaces or incomplete information. And don't accept the application until it is completed to your satisfaction. Someone who is out looking for a place to rent and isn't prepared to provide all the information on the spot has one strike against him or her right off. If they don't have the information right there, refuse to accept the application, make them take it home and find it.
Most renters know what's on a rental application.
Under no circumstances should you accept the application and wait for them to call you with the information to fill in the blanks. You must be able to verify all information on the rental application. No exceptions here. Bad tenants will try to use friends and relatives to act as landlord and employment references. Addresses and phone numbers have to match.