I am not a LA but from reading on QB some of the basics are....Trim all the loose threads on the back, make sure all the seams lay flat, make sure the backing fabric is 4-6 inches larger than the top(someLA like even more) no seam in the back or the seam running crosswise not lengthwise.
Ask to see samples of their work or pictures. Ask the prices for pantograph(basic) or custom quilting. Ask for time frame for pick up. Some LA prefer to supply the batt and thread and some don't. If you can visit where your quilt will be quilted. Is it pet free and smoke free if you have allergies? That last time I got a basic queen size quilt done it was $150 and that was over 5 years ago. Some of the LA from QB may give you some more pointers. You can find people on QB who do quilts in your area on the main board list.