Write the next sentence in this paragraph:

How to find a good plumber
Check to make sure that they have a plumbing license.
The most basic rule is to be sure that they're licensed and carry full insurance that protects you and your neighbour's property in the event of a catastrophe.
Get two or more references and read online reviews.
You can even ask to see some of the work they have done. Read their facebook page and twitter feed to see how they are interacting with their customers Ask how long they have been in business for.