Give tenants plenty of notice of any proposed rent increase. This will give them an opportunity to prepare for the increase, and will make them more likely to accept it.
Offer tenants incentives for accepting the rent increase. This could be in the form of a rent discount for a period of time, or offering to pay for certain utilities or services.
Make sure the rent increase is in line with the local market. It won’t do any good to raise the rent too high, as it will make it difficult to find new tenants.