Use a desktop document system or a word-processor to print and make copies of a simple form. I keep mine in a binder and when the quilt is picked up, the intake sheet is filed chronologically for handy reference at tax time.
For the intake sheet, put your name/business at the top with contact info, then customer name, address, phone, email, date of drop-off and the date the quilt is finished.
List all info needed for the top--dimensions of the top, type of batting (purchased from you or brought, along with dimensions of the batting) and the dimensions of the backer.
Leave a space for notes on quilting designs. Here I list colors/block patterns of the top and any thoughts or suggestions from the piecer. Comments such as "no feathers" or "not girly" go here. Listen to what the customer says and doesn't say. If they say "do what you think is best" delve a little deeper and ask about the recipient--age, sex, preference of density of quilting, etc. Know the batting and what it will do when quilted densely or less dense so you can steer them in the right direction.
List an area for thread choices and a place to put the thread charge if you will charge for it. List both top and bobbin thread.
At the bottom is a list of all charges--thread, batting, seaming a backer, turning the top, quilting, etc. It is all broken out and then sub-totaled. We charge sales tax in Washington so that is added, with the grand total at the bottom.
Then there is a statement at the bottom---" I authorize Kerry's Beautiful Quilting to perform the work listed" with a place for the customer to sign.
If you like I will send you a copy of my intake sheet to your email address. Let me know if you would like a copy.