Sometimes seldom used cars can be used to advantage. Having cars randomly moved around between several houses can go along way to confusing the issue on exactly who is, and who is not, home. In my experience every third household seems to have one too many vehicles for the driveway space and many of these people are willing to rotate parking around neighboring houses. A local development, and its ever-loving homeowners association, has a rule about having more than two vehicles. Moving the extra car around helps keep both thieves and and HoA off balance.

I don't place much faith in alarms. Even the 'armed response' services are highly questionable. Even if the have a response team close by, most won't, you also have to consider their motivation. Rent-a-cop types are known for their macho airs but push comes to shove they are usually smart enough to be slow to respond when it comes to facing down a robber. A thief that might be armed and on crack.

If they get there late they can lament the delay as they fill out the paperwork. Getting there early means they might get shot. You can sort of figure out which side of that they are going to lean toward.

Audible alarms usually scare off kids and amateurs but professionals will know the police response times and be in and out in half that. That assumes they don't bother to disable the alarm.

A radio playing and lights on timers can help but you need the noise to be loud enough to hear but quiet enough that they can't easily tell it is a radio.