the more physical shit you put on your car...will usually deter theives away.

such as auto-lock, shifter lock, steering wheel lock and then you can goto the kill switches and alarm is a must. (if you get the steering wheel lock i have, it makes a pretty good weapon)

clean the interior of your car, make it spotless, keep everything in the trunk.

try keeping the interior fairly stock.

as far as the embelm stealing goes...just shave the embelms