[noize]

Another good technique would be to carry a large empty box, use a bit of acting to make it look like it's heavy and you are struggling, then walk up to the door as someone is going through. Get their attention as they pass through and they should naturally hold the door for you.

Even Kevin Mitnick explained this in The Art of Deception.

Thanks for that I knew I had read that from somewhere but couldn't for the life of me remember where, although I don't think I read the entire book. I'll have to find it sometime

http://www.scis.nova.edu/~cannady/ARES/mitnick.pdf

Great book about SE. I'll read it just as I'm done reading The Art of Intrusion, Ghost in the Wires, Hacking: The Art of Exploiting Second Edition, No Tech Hacking, TCP/IP Clearly Explained Fourth Edition, a few of the programming/cryptography/reverse enginering books I have in my e-library, some low-level book and Hitchiker's Guide to the Galaxy. I hope to remember them all.