Doors are always locked... nothing is left in plain sight... trunk is almost always locked to where you can't open it from the inside - just turn the key the opposite way & feel the "click".
If you have an NA that doesn't have the remote trunk pull disabled feature then you need to look on the board for the modification to the lock cylinder. It's easy to do with a dremel tool. I did it on my 92 B&T and it worked nicely.
That way if they do break into your car then they can't get into the trunk. Oh, and I always leave the glove box and center console unlocked since they are easy to rip open & break.
RJ