A while ago some cars in my area were knocked off and dad went a bit nuts about security particularly because we are on a bit of land so this is what I understand...
Most thiefs are amatures. Take yvettenjosh. If they were going to do it properly or were associated with APS why not choose someone with a bigger collection. I havn't heard much about the break in style but it sounds pretty unplanned from me (some young people out and looking for something to do IMO.)
Because of this, a lot of deterance is about appearance. Thats why lights are left on in public places a lot, to deter vandels. Big dogs that bark, even if they are friendly are excellent as well as a sturdy fence and gate around the property.
Also (and I am not sure about the cost of this) you could get an alarm intended for a larger property. Friends of ours on a kiwi fruit farm in NZ (approx 40 ha) have one that phsically hurts your ears if you are in the house when it goes off ( I know
I set it off ). You don't have to go this far but its an idea to be looked into...
Also there are also products out now which allow you to place an infrared beam across you gate. This is linked to a speaker in the house and this speaker beeps when the beam is broken. ie when a car drives in or person walks in. Of course this only works if the person comes through the gate...
If you are going away for a holiday and can't find anyone to house sit then organise someone to mow the lawn/check the house and pets, leave a radio going, and hang some old clothes on the line. Nothing screams break in more that an empty looking house day after day.
These are all just little things I have picked up.
Another one is keep stuff away from the main windows of the house where people walking/driving past cant look in and see it.
This is really **** as before I would have loved to meet some people from here and their collections so I can satisfy my serpantine lust, but now I totally understand why no-one would want to invite some stranger into their home. Because of a few we all suffer...