Here are the steps I use.
I never use small print, everything with the customer is upfront.
I do a walk around with the customer with my vehicle work sheet. This has a drawing of a car on it and i can mark down and damage it has on it.
I look inside and mark down any damage to it, tears, cuts, burns.
check the tires for any cracks, check the rims around the edges for parking marks
After i walk around the complete vehcicle inside & out, i have the owner sign the work order which allows me to start the detail job and informs the owner of all the damage that was on the vehicle prior to briging it to me. This is a real good thing to do and it really does cover your butt.
The one thing i make sure that all my customers know is that i am not a miracle worker, I am a detailer. There is only so much you can do to car, before it has to be painted. I also have on the vehicle sheet a note to the customer that the vehicle will not be released until the job is paid in full and that i do not take credit cards.
If you want to see some of the forms i use, let me know i can email them to you or any one else looking for some help.