I had my attic and exterior walls insulated with cellulose, but I think the research approach I used might work for you.

First, try to find out what type of insulation is correct for your project, then try to find out who makes the best version of that insulation. Next, call the insulation manufacturer to see if they can suggest an installer.

I started at www.cellulose.org, went to www.nationalfiber.com, and was referred to http://www.aainsulationinc.com/. It was so easy I was suspicious of my good fortune. The house was warmer and quieter before the job was even half done.

We use Angie's List. Unrelated: It's not only helpful for finding contractors, but I've also used it to try and get somewhat of an idea of what something might cost when I haven't the slightest idea. A lot of the reviews include the cost of the job and reading the description or comments can give a bit of an idea of what was done. Not at all accurate, but when you don't know if a job costs $500 or $5,000 it can be a starting point.

For our insulation we cross referenced Angie's List with the list we were given by our energy auditor.