If you go to
www.estatesales.net you can look up your area and see who conducts sales, then start calling to schedule [free] appointments.
A few suggestions: Interview a few companies... get references and call them... also go to sales and see how each company conducts and how well they set up the sale, staff, etc. Do they conduct full-time or part-time? Look for well experienced professionals with a thorough contract addressing exactly what they do, so you have more to go on than just a hand-shake. Lastly, remember the old saying "You get what you pay for". Although pricing is generally competitive, cheaper rarely means better. All the Best!