I have done the VAT refund twice and it was different each time.
In Paris they made two credit card charge slips, one for the purchase and one for VAT. The shop then gave we the form and a self-addressed stamped envelope and told me to get the form stamped at the airport and put in in the mail there. If they did not get the form in a week or so they would process the charge for the VAT.
In Venus the shop gave me the form and said get it stamped and then take it to the Forex money exchange booth in the airport to receive a cash refund. The drawback to this method is that Forex takes a percentage for their trouble and if you want it in $USD they charge a money exchange fee.
In both cases I had to find the VAT booth, which is located outside of security, before heading to my flight.
It only pays to mess with it if you buy some expensive items, so my advice is stay out of jewelry stores and other shops selling small expensive items.