I've been using hospital parking lots to park at night with a good degree of success for the last year.

I like doing this because they have good security, and are usually pretty cheap. For the 5 bucks a night, I find the peace of mind to be worth it.

My advice is to change your parking spot every couple of days, and at night, stay in your vehicle and be as low key as possible. Also, learn the relative schedules of the security guards, as they usually have one of their older guys walk around just to get eyes on things.

And know where the cameras are and where they're pointed.

I prefer parking structures over parking lots, because you've got a roof over your head, and it's easier to blend in, as employees usually congregate in a single area, and that's where I'll park.

Good luck.