The first order of business is attracting good tenants to begin with. That means that not only does the house show well but it's got the normal features expected for its market; garage door opener, high efficiency HVAC, solar reflective window screens, attractive landscaping, good quality appliances and fixtures, nice decor touches.
The best thing I ever did for keeping tenants longer was to require a minimum two year lease going in. Once I did that my average turnover went to five years.
Gifts are not the answer, it is all about finding good tenants at the beginning, but if they're too good they may eventually move out and buy a home of their own.