Consider using Rhino. New leases and renewals sign up for Rhino, which then handles security deposit expenses and collections.
Set a number, typically above inflation
Limit rent increases to one a year, similar to how most people think about wage increases
To retain tenants, under cut street rent by 4%. For example, new tenants would be charged 4% more, but this would cut back on move out
Warn give 2 months lead time on rent increases
Use odd dollar amounts, 31$ vs 30$ because it seems similar to expense increases rather than just profit increases
Adjust for desirability
Graduated rent increases, split the increase in two
Test increases on vacancies first not renewals
Actually do value add before rent increase
Charge for apartment improvements
Offer improvement package
Downgrade tenants through backdoor