Be polite refer to her as miss his last name--please and thank you compliment something in her home or what she is wearing and keep your hands to your self or be overly affectionate till u get to know her better...first impression is everything
of course she is going to be happy to meet you, ask about his childhood! were they grew up, was he living in poverty, is their signs of drug problems or drinking that might effect your relationship!
are the parents well dressed people or getto? these are the things you look for and if you are content with that than go for it ! i do think you need to find out though if he is allergic to anthing as well as emergency contacts?
seriously ? drug problems, emergency contacts, allergies ?? you ask all that to ma, and not the guy himself ? if the guy wont even tell you the truth about such things, whats the point of things things as far as meeting his mom!
your right tell him your not going! you forgot you had a previous engagement! and go home and do not answer the door or phone
let her talk. you listen. you'll know what she likes to talk about, her interests and stuff. let her tell stories to you about your boyfriend," aww, when he was a kid, " types, help in the kitchen, compliment on food, be nice. genuinely nice.
Relax! She just might love you! :)