When you are having any work done you need to make sure that you find the best person for the job. You want them to be able to do a good quality job at a reasonable price. This is easy to say, but can be more difficult to achieve.
The first thing to do is to speak to anyone you know who has had work done on their property and see whether they can recommend the people that they used. They might be able to give you contact details or tell to avoid certain people or companies.
You may like the idea of using a big and more well known company because you think that they will be more trustworthy or you may like the idea of using a local tradesperson so that you get a more personal service. It is worth remembering that these are stereotypes though and so you may not get what you expect.
You will find that there are some websites for tradespeople where they get listed. On some of these sites, they will only get listed if they are considered to be good, hold specific qualifications and things like that. Bear in mind that some lists you can pay to be on, so they do not stand for anything, so look into things carefully.
Looking at their website and customer testimonials could help you, although it is worth bearing in mind that they could be made up! You may be able to find review sites with information and you could always just look up their name and see what comes up in your search engine as anyone really bad might have been mentioned on there.
It is worth spending a bit of time researching the person you get to do your work as you could end up paying them a lot of money and you do not want to have badly done work for it. You also want to be able to trust them and feel happy having them do the work for you.