Tips & Tricks for infiltration?

[Curious George]

I often find myself being questioned by residents when I try to get into live buildings.

Most of them tend to be pretty relaxed about it, and telling them I'm visiting a friend lets me trough, but some of them are more unpleasant with questions like "Do you really live here? Let me see your access card" and things like that.

Any useful tricks for getting in, without being bothered by people?

 

[skeleton key]

Best always to be discreet but if you get rumbled as happens to everyone just be up front about what you are doing