In an open parking situation like described here, the first step is to reduce the amount of attention the bike draws. Take it easy on the throttle in the parking lot- nothing screams "Steal my bike!" or "Fuck with my ride!" like a yosh pipe at 8,000 rpm. Next, put a cover on it. Yeah, it'll help protect the bike from the elements, but more importantly, it'll keep it out of sight from anyone driving around looking for targets. Disk locks, cable locks, and alarms are just going to stop the local punk or junkie from taking or messing with your bike. These will not stop a pro that wants it. LoJack is pretty good for getting stuff back, but thieves will usually rack up a decent amount of damage pretty quickly so you'll still be paying out of pocket. The only way to completely protect your bike is to insure it VERY well.