I want to build a little circuit to detect vibration of the glass in a window pane. I was told that a Piezo may help. Can anyone suggest what general parameters of a piezo I should look for in buying some for this application ?
The better ones for such application are the "unpackaged" ones as they allow a wide contact with the glass surface, see: https://www.sparkfun.com/products/10772
The kit looks expensive to me, you probably can hire such piezo on Ebay for few bucks or even scrap them.