Generally, don't call owners before 8am or after 9pm. Dress appropriately when you go to look at the property. Remember that while you are checking out the property the owner is checking you out as well. Their sixth sense about tenants can be as important to them as your credit history. If you make an appointment to see a place, be sure to keep it or call to cancel.
Verbal agreements can often lead to misunderstandings and missed opportunities.
Keep copies of all receipts, deposits, rental agreements and leases.