First and foremost, the best styles of locks are the popular U-Lock or a hefty metal chain lock. The cable style locks can be a deterrent, however, they can be cut quite easily. Although they are a little more pricey and heavier, I highly recommend the U or chain style locks over the cable style.
Depending on whether you are in a high risk or low risk area you can choose how thoroughly you want to lock your bike up. The most simple way is to place your bike next to a pole and run the U-Lock or Chain through the front wheel and frame at the same time, and then through the pole itself. A cable lock can be a nice partner to a U-Lock as shown below:
These photos are courtesy of Kryptonite Locks.
The most secure way would be to remove your front wheel, line it up with the rear and run the U-Lock through both tires and the frame. This will entail disengaging your brakes on most bikes, see your local bike shop if you do not know how. Locks are sold at all local bike shops and they vary by brand in size and locking mechanism (combination or key). Hope this was helpful, please let me know if you have any questions about this or any other topics you would like discussed.Leaving your bike parked outside is always a risk, but with a good lock and a few other tricks, the risk can be lessened. Use the best lock you can afford and always lock your bike TO an immovable object. Try not to leave your bike locked in the exact same location every day, or for a prolonged period. One view is that an old ratty-looking bike is less likely to be stolen, but I am not sure this has been proven. Olympia Police have told me that most of the bikes stolen here are lower-end bikes that have been left unlocked. If your bike is stolen, DO report it to the police. A significant number of bikes are actually recovered. It helps to have recorded your serial number, and to have a photo of your bike! You can also register your bike at nationalbikeregistry.com