Although this is a service for professionals, it's vital to remember your customers are just ordinary people wanting extraordrinary services. Greet them by their individual names when you message them! They are a person, not just your next paycheck! You always want them to feel as though you are a friend helping them.
I'm a Thumbtack Top Pro. The best tip I can give in in your follow up. I ALWAYS follow up and when I do, I include recent pics of my work correlated to the customer's request. For example, as a professional makeup artist, if I receive a request for wedding makeup, I follow up with pictures of my recent brides with the look that favors that of the request. I include multiple nationalities and complexion shades to show my diversity. Including pictures makes it easier for the customer to see your work and prevents them from having to look through 100s of pictures on your profile to find what they're looking for.
Followup. Followup. Followup. As a DJ, I continuously go through my Inbox and Requests to followup with dates I am available on. Every so often I will get a reply from a customer that hasn't made a decision yet....and land the gig.