It HAS to fit over my shoulder - not as easy as it sounds as I am not a petite lady by any stretch of the imagination. I can't be doing with carrying bags as I need my hands free.
It also has to be easy to use, one handed opening is great. Flaps work SO well for me.
I'm also rather partial to chains
And the feel - I haven't got a caviar (yet) for this very reason. Lambskin or soft, soft leather.
Colours - haven't got that far into my obsession yet, but would kill for a lovely purple and a red. (I don't like the dark colours this season)
In roughly this order:
1) Colors (Red, metallics... Bright ones)
2) Flap (just love the chains, interwoven or bijoux)
3) Size (big ones before small ones)
1. What type of chains and it need to go over my shoulder ( have 2 little girls )
2. Color
3. Size
4. Price ( this should be first but if I really love it, sometimes price does not matter )