It really depends on which way you want to go. Do you want to just scare them off or actually catch them in the act? To scare them off, you cant beat a few different alarms both on the garage door and motion detectors once inside. A security post is a good one, but it must be on the inside of the garge door really, so it dosnt draw attention.

If you want to catch them in the act, then use a security light that sounds an alarm inside the house. Best to take the bulb out the light so they dont even think that your on to them and carry on as normal whilst you have time to get dressed and grab your weapon of choice.