The first thing to do is have a sit down conversation with customer and discuss basic prices of fabric and how much it will take. Most will walk away after learning how much it will cost in just materials. If they don't faint right there, the next step is to determine exactly what size they want in inches....there is quite a bit of difference in what one person says is queen size and the next. You also have to decide on a pattern, fabric colors. quilting style, batting preferences (some want very warm, some want lightweight, some want poofy), quilting thread color, how quickly they want quilt versus how quickly you can make it, and lastly add in your labor (don't shortchange yourself, but don't overprice either)....and get all this in writing. Then tell them that you need the cost of all the materials in advance....non-refundable.....balance due upon completion. Have the customer sign the paper showing all details and that he agrees (even for best friends). I am sure there are probably details that I have left out....but you get the picture.....everything in writing, assume nothing.....this way you are covered if customer defaults on final payment (you keep the quilt).
If after all that, and the customer still wants to proceed then you can rest assured that they understand the true value of a handmade quilt.