As any homeowner will tell you, if something major is going to break, it will happen on the weekend. That's so you can spend hours trying to find a tradesman to fix your problem and then spend double-time paying for the repairs.
A Trustworthy plumber will answer all of your questions. Good plumbers will provide you with references, and tell you how long they have been a plumber, and the type of guarantee they provide for their work (warranty.) As well, a professional plumber will offer emergency service for nights and weekends. You should be able to make contact with him or her in a timely manner. A professional plumber will also have all of the appropriate insurance such as liability insurance so that you are protected in the event of an accident.
When you contact the actual plumbers that you have on your listing of emergency numbers (which might very well be the first page of Google) be sure to learn how quickly they will be able to get to you. The sooner the better is always the general rule to go by. You don't want to sit with the issue for the next few days, even a few hours might be too much to ask in some situations. The best plumbers will be the ones that can get to you the quickest.
Check the burner switch. Usually located near your furnace, it looks like a light switch with a red switch plate. Sometimes this gets turned off by mistake.
Here's an example. Let's say you are a plumber. Will people put "plumber" into Google to try to find you? How about "plumbers"? How about "slow drain"? All of these are valid search terms, but they each reflect a different "conversation" in the mind of the searcher.
Sometimes repairs do not need to be immediate, but they should be quick. When you do not need emergency repairs, but cannot wait days for help, you should find a plumbing company offering same day services. This means you can call in the morning and have someone there to make the repair within hours. Since some companies do not offer emergency services, same day service may be the next best thing, so you should look for this offering if it is the best your Local plumber has.
Certified. Just like any other professional, a plumber comes with a certification. Make sure that you hire someone that is fully certified as a plumbing specialist. Never assume that all plumbing companies that offer these types of services come with a certification. Do your research.
Even if you have not noticed a problem with your sewer lines, consider calling in a plumber for an inspection. If there is a problem, set up an appointment to have it repaired right away. Remember that replacement can be costly but you can save money by going with a company that will avoid trenching the yard.