I use a minimum security lock and park where I can keep an eye on the bike. It's just a little $9 REI cable with a combo lock, wouldn't slow down a serious thief for more than a minute or so. Fortunately, though, here in suburbia there are lots of convenience stores and coffee places with racks or railings or something outside to lock to.
When the occasion arises, I also have some stouter hardware, but for day-to-day rides it stays home