bicyclists’ golden rule: ‘never buy a stolen bike…’
Ten Commandments of Bike Theft Prevention
I. Remember that your bicycle, no matter what type or condition it is in, is valuable and sellable merchandise to the bike thief.
II. As you ride, be alert for the possibility of an ambush.
III. Ideally, never leave your bike outside, locked or otherwise.
IV. If you park your bike outdoors, don’t leave it for long.
V. Outdoors or indoors, even in your home, lock your bike to something.
VI. Keep up with the latest anti-theft techniques by sharing horror stories with other cyclists.
VII. Be on the lookout for bike thieves. Anywhere many bikes are regularly parked you will eventually find bike thieves.
VIII. Register your bike, and carry its I.D. and serial number on your person.
IX. Report your stolen bike to the police, registered or not. Carry the police report number with you in case you spot the bike.
X. Don’t be afraid to press charges against the individual who bought your stolen bike. Bike theft would largely cease if people stopped buying stolen bikes.
– Taken from Frank Gresham, “Save Your Bike,” City Cyclist, November-December 1988.
The Broken Spoke 
Give me an old cool bicycle, and I’ll ride around the city for days.
XI. Don’t buy a bike you don’t intend to use and then leave it in the same place all winter. Thieves hate to see a good bike ruined by neglect.
XII. Look around. See all the bikes laying about randomly? Those were the unlocked cheap ones stolen by criminal idiots. Your nice specialized hard rock will be taken care of; just not by you. If you locked it, anyways…
XIII. Seriously. DO NOT put your bike in the racks in front of your building unless you have absolutely no other choice. All your neighbor’s friends and everyone else can scope it out whenever they want, and come back anytime.
IV. Stickers. Everywhere. Bike companies love to advertise their products for free on your piece. This also makes for easy spotting of expensive bikes by anyone with eyes. A bike covered in stickers surrounded by huffys and Schwinn’s will be harder to spot than a gleaming aluminum trek will. Unless you really do like to show off your bike, stickers could keep it yours longer. And they’ll also protect the actual finish from light abuse.
XV. Since you’ll never spot a bike thief before they strike (unless they are really, really stupid and should therefore be caught anyway) invest in the best lock and cable/chain you can. Otherwise be prepared to discover your bike missing when you get up in the morning (or take it with you wherever you go).
* Not a bike thief, just keenly aware of the possibilities