Sheldon Brown’s Lock Strategy is often referred to as a preferred method for ease and security. It involves using a mini u-lock to lock the rear wheel to a bike rack between the rear triangle of the bike frame. This accomplishes two things, it secures the rear wheel (2nd most expensive part of the bike) and the frame cannot be stolen unless the rear wheel is completely sawed through. See Sheldon’s page for detail.
In real world situations I’d say it’s not likely a thief is going to saw through your rear wheel, but as this Youtube video shows, it can be done quite quickly. My main gripe about his method is that visually, it doesn’t look as secure as it could.
Lastly, Sheldon’s method does not secure the front wheel. This isn’t a significant issue if your front wheel is bolt on, but most bikes these days use quick release wheels. Sheldon’s method leaves your front wheel vulnerable.
As such, this is my modification of the Sheldon Brown Locking Strategy.
This shows an OnGuard mini u-lock securing the rear wheel and frame (via one chain stay). The front wheel is secured using a 4′ accessory cable. It is locked to a 2″ pipe, the same diameter tubing used for most bike racks. If you lock your bike like this, chances are it’s going to be the most securely locked bike on the rack. Now, cables can be cut using a hand tool in less than 30 seconds, but I feel comfortable saying that many thieves will not cut a cable just to steal a front wheel, unless your front wheel is really nice. If it is, I suggest an additional u-lock for the front wheel. Alternatively you can purchase a long shackle u-lock, remove the front wheel if quick release, and place it next to the rear wheel and secure it with the u-lock. The Kryptonite Evo lock is also very popular. If you plan to carry an additional u-lock for the front wheel and weight is a concern, consider the lightweight Palmy u-lock.
To prevent quick release seat theft, remove the seat from the bike and thread the cable coming from the front wheel through the seat rail before looping it into the u-lock. Alternatively, affix a seat leash.