As a home owner its really hard to know if a tradesman you choose to fix a problem in your home really knows what their doing.
I work in the trade industry, on average, I go into 3-8 homes per day, they tell me of situations that have happened in the past when they have requested services of trades to come out to their properties for a specific trade related issue, they ask the tradesman for a price to investigate/repair a certain problem, and accept the hourly charge for that tradesman, If they are unsure of the correct solution due to lack of experience they will take more time (which means more money)and instead of knowing how to fix the problem they will try a half arsed attempt to fix the problem, they then charge for their time and materials used, walk away and you find the problem is still not fixed, and in some cases the next tradesman you get may have to fix their f-ups.
This ends up costing you more money and hassle because the problem is not fixed.
So what do you do as the paying customer?
Ask how long they have been a tradesman, and how long they have worked for company.
Never pay a tradesman in full upfront.
Don’t pay cash until you get a receipt.
You could ask for their contractor licence.
Ask about a warranty on work.
If it sounds way to expensive then it probably is, remember if its not urgent you can get another quote.
Usually if a tradesman is recommended they are good.
As a tradesman I am concerned at the level of experience some tradespeople have, I have worked for a company for 16 plus years, I find that I am always learning, experiencing new problems and growing as a tradesman and I feel that working for a larger company I can always refer to an employer or a fellow work mate.