This will give you a better understanding of what kind of questions you might want to ask the contractor when he visits your home. It will also give you a better understanding of what's happening when the job is in progress. Even if you feel you already know, there is always the possibility that you might have overlooked something. Once you have an understanding of what the project is really about you need to decide who would be most qualified to do the work. So why hire an electrician to replace your roof.
Skilled labor is exactly that.
And getting the right person to do the job is important. Sometimes paying a little extra to get the person that's best could save you a lots of time and money in the long run. And by understanding your project you will then have a better understanding of who is best qualified to do the work. You understand your project and you know what you need. Now its time to list some contractors.