Five tips for safely locking your bike
In my student days I never bothered to get a really good bike, because you'd know your bike would eventually get stolen. Ok, maybe some better locks would have helped,
Lock your bike to a fixed object
The number one rule is to lock your bike to something that is firmly attached to the 'outside word'. This prevents thieves from just grabbing your locked bike, and loading it into a van. You can attach it to a bike rack, a fence, a tree or a pole, but make sure the object you're attaching too can't easily be taken along with your bike. Or in the case of a pole: make sure your bike can't be easily lifted from off the pole.
Use different types of locks
One of the most effective ways to demotivate potential thieves from having a go at your bike, is to use different kinds of locks, so a thieve needs several different tools to steal your bike. For example, if you combine a chain lock with a U-lock, a thieve would need a heavy-duty bolt-cutter for the chain lock and an angle grinder for the U-lock. This makes it tool heavy, slow and noisy for a thieve to attempt. Combined with safety measures that already come with many bikes (like a ring-lock or an electronic lock on e-bikes), there's a good chance a thief will look for an easier target.
Be mindful of where you lock your bike
Where you leave your bike is also an important factor: theft is a performance, and audiences deter it. So always lock your bike in a busy, well-lit, visible area. Use designated bike parking where available. At home, take your bike inside if possible.
Look for the ART rating (Europe)
But how do you know if a lock is actually secure? In Europe there is the ART rating system that is run by an independant foundation who rigorously test locks. For most bikes look for at least a 2- or 3-star ART rating, or a 4-star rating for expensive e-bikes. You can also check if a lock was actually rated by ART, by filling in the brand and model number on their site.
And even though ART-rated locks are generally more expensive, there or brands like Walfort (sold by Action in Europe) that sell a 4-star ART-rated lock at an affordable price.
Customize (or heavily use) your bike
If your bike has many custom or mismatched parts, looks heavily used or damaged, or looks uniquely yours, it makes it much less of an attractive target for resale. Use your bike heavily, and suddenly those scatches and dents might be the one thing that keeps your bike yours.