With the large number of bike thefts in my area recently I have been taking security even more seriously (If that is possible...is my paranoia protecting me or inhibiting me?).
These are the measures I take and it's sad that I have to...
Never leave an expensive bike unattended anywhere.
Tape over logo's etc on my commuting bike, make it look like a "loaner"!
When possible use a bike with bolt through axles, bolted seat collar and no qr's anywhere...make the thieves bring tools!
Buy the best lock you can!
Do not think bikes are safe at home, use the same precautions you do when out and about.
Check your insurance.
and lastly...enjoy your cycling and don't let them win!