In his famous and interesting article "Ten Simple Rules for Selecting a Postdoctoral Position", author Philippe Bourne states, in the 2nd point:
Rule 2: Select a Laboratory That Suits Your Work and Lifestyle
If at all possible, visit the laboratory before making a decision. [...]
I think that is definitively a good advice, not only for Post-Doc applicants, but for all applicants in general. But, what is the best way to arrange a lab visit?
What to do when you're there?
Whom to speak to? What to ask? What to do?