I manage properties in 3 states. Each have different laws regarding how much and how I formally have to notify tenants. In California if you raise it by anything over 10% you must give 60 day written notice. Most states just require 30 day notice.
A good landlord checks for current market rates and makes rental increases accordingly. Remember it is a business and you need to be competitive. However, it is a business so you want to make money. I would make sure that you do an annual survey and pretend to be a renter. You quickly find out where you stand. If pretending to be a renter is hard, then go ahead and just ask the landlord what they have and what they charge since you are trying to determine what rates you should charge.
This is all important because NAR and other agencies are expecting the next three years to be higher than norms for rental increases. Rental increases generally are around 2% above CPI. that means around 5% these days. However, since the home market is slowing many landlords will get 5% to 10% in many markets.
if you have not kept up with this you eventually have to give someone a big increase and then you loose them as a tenant. We always increase each year even if just by a tiny bit to keep tenants aware of procedure.