Ask around. Ask your friends, ask your neighbors and get referrals. Nothing is more powerful than the testament of someone who has had a local plumber in their home and can speak to his/her capabilities.
Television or radio - There are many plumbers that will put an ad on the television or local radio stations to let people know they are available for hire. Pay attention the next time you watch television or listen to the radio because you never know when you will hear about the right plumber that you can hire.
Make sure you get all the technicalities right and don't pay the full amount until the task has been completed. Stay in the loop and keep checking-in on the progress of the work. You have to be firm if you don't want to be cheated into accepting poor quality toilet repair for high costs.
Not all faucets have or even need interior shut-off valves. If your valve is a "frost-free" style of valve then you wouldn't need a shut off inside. Frost free valves are a style of valve in which the Trustworthy plumber water shut off for the valve is located internally in the valve inside the house. The use of a frost-free valve is best suited for locations in which an internal shut off valve is inaccessible such as a location where the walls and ceilings are all finished. This style faucet can leak over time. If you have a frost-free valve that is leaking you will need to replace the washers internally on the valve to prevent the valve from freezing and bursting.
Call a Local plumber to set up an appointment for an inspection. You will need to be home for this service and when the work is complete, you want to be available to find out what the professional found out. If there is work to be done, depending on the severity, it might be a good idea to go ahead and schedule the next appointment for repairs.
As precautionary measure, you have to tell all your tenants where their individual water shut off valve is located, as well as the entire building's so they can turn it off in case of emergency. And don't forget to make them accessible. It won't do any good if they know where it is but it's locked and they can't break in.
Once the work has been completed, ask for a breakdown of the bill before it's paid. That way, you know what you're paying for and it stops the plumbers asking for more money down the line.