The best deterent is a sticker on the outside of your door warning potential thieves that the garage if protected by security company ???. If you don't have a security installation, no problem. Go to Office Depot and buy some printable sticker paper. Create an official looking security logo and print it. No thief is going to question whether the company actually exists. They will immediately move on to easier targets. This is the cheapest form of theft deterent. Make sure you put it on all access points into the garage including windows.