[lbook]

I do not have any first-hand experience with it, but here are my two cents nonetheless:

It depends on how their returns/service desk works. If you can, check it out during a busier period when people are returning goods. If its a bigger electronics store, for instance, just lurk around the area during a busy time and take mental notes of the procedure. If it's a quick "scan, show receipt, receive the refund and leave" like in most bigger chain stores, a fake receipt may suffice. If it's a $2k HiFi system from a specialised store it is likely going to be more difficult.