when i met my wife, she had tried anal twice and once it was more of 'ok its in, now get it out'. she wasnt very receptive, no pun intended, to the idea. i had only enjoyed it once before but was a little more experienced with finger insertion and analingus. she said no way to both.
one night whilst going down on her i licked a little farther down and gauged her reaction. and it was good. i kept working in wider circles til i was tongueing her pretty good and she was obviously emjoying it. afterward we talked about it and she was a little suprised at how good it felt. i said 'i told ya' with a sly smile.
from there other avenues opened up and one evening while in the spoon position, she reached around and introduced me to the back door. quite shocking!
there's been alot of great advice here and if you just follow it she might decide that it's something that interestes her.
major points:
1. patience
2. pleasure
3. patience
4. lube
5. patience
6. start small
7. patience... espcially if you get to that final step.. let her control everything.