Good plumbers are going to have a valid license that you can check on. Look up the number they give you online and see trustworthy drain leak repair if it is valid and if any complaints have been filed against that number. This will tell you if they are at least good and have not done anyone anything wrong. Some of the best plumbers are going to know and understand the local building codes and will be able to explain to you what is needed for the job to be in code.
If you ask and don't receive a copy of worker's compensation and liability insurance, don't use the builder. You may even go as far as to call the agent listed to verify that their insurance is in force. Finally, remember worker's compensation protects people. Liability protects property. You need to have both.
It is always a good idea to do some online research. For example, if you have a clogged drain and you live in the Atlanta area you should search for "Atlanta plumbers" or "Atlanta drain local water heater repair service". This will bring up a list of Atlanta plumbers rather than plumbers from across the country.
Pool developers consistently experience a high turnover with their staff so it's a constant struggle to keep good, experienced people who have installed a lot of pools. There are also a lot of developers who will sell you a pool with no regard for how it will be integrated with your landscape and lifestyle.
Next remove your spark plugs and use a can of spray fog for engines. Then replace your spark plugs clog and turn the engine over to coat the entirety of your cylinders. Note that you should not actually start the engine. With this done you can treat your fuel with any stabilizer you choose, just be sure it is a reliable brand you can trust. Follow the mixing instruction for your specific brand; don't forget to give it a good shake if you're pre-mixing it in a can!
You definitely want a plumbing service that has access to any type of parts that a given job might require. If they do not carry them in their trucks, you want a worker that knows where to quickly buy them. Nobody wants a repair person spending the better part of a week trying to track down some special drain part. While a lot people do not consider this, it is very important.
Remember, there is a million small ways this is communicated. Company uniform, company vehicle, logo, website, slogan, elevator pitch etc. Get the details right, and make sure they are working together to create a consistent image. Ask for feedback from customers, friends and family, even total strangers if you have to. Ask them what they think of your logo - what does it evoke? What do they think of your company name? Objective, third party feedback is your best source of information on how the public perceives you. A good image is crafted slowly over time.