I second sc00ter's recommendation of the Hiplok Gold chain/belt. I use both the Hiplok and an ABUS Granit X Plus U-lock to lock up my bike when I go to the office in downtown Toronto.
If I'm on a short grocery run or errand I will just use the Hiplok.
In no particular order I follow these general guidelines to secure my bike:
1. Use 2 locks, each of a different type i.e a Heavy chain and a U-lock.
2. Park next to a good bike with a crappy lock. A thief will probably take that one and leave yours.
3. Never park on a university campus or at subway or train station as these areas are frequently cased for good bikes.
4. Park near a security camera if you see one. (I have line of sight from my office so I have a security camera trained on my bike from my window.)
5. Try to and make sure whatever you lock your bike to is sturdier than your toughest lock.
6. Remove your battery if you can. (Most pro thieves that have the skills and tools to defeat an ABUS U-lock or a Hiplok know that ebikes are nearly worthless without a battery and will avoid them)
7. Lock your frame and front wheel with one lock to the post or rack and go through the rear triangle and wheel with the second lock. Or if you only have one lock, lock your frame and a wheel to a post and use a cable to secure your wheels to the main lock.
8. Remove your seat when parked or secure it with an ABUS Nutfix or Pinhead device so no one steals it.
9. But don't just worry about the pro thieves, remember there are drug addicts roaming about who will steal your seat or any quick release wheels to fund their habit. Your $500+ rim, tire and cassette or your $200 seat and post they will sell for $10 just to get a hit.
Cheers!
Here is a picture of my bike with it's thief's nightmare lock combo: