Really your best bet is to use a U-Lock like has been suggested.
HOW TO LOCK YOUR BIKE
Locks ranked from worst to best
Some of these killer locks also come with guarantees that your bike will not be stolen up to with the Kryptonite New York Fahgettaboudit U-lock $4500, easily enough to replace any motorbicycle.
Oh and Amazon has a huge selection for probably the lowest prices you'll find.