i look for the STYLE, if it's easy to match with all the clothes i own,
how in season it is.. i wouldnt want to buy a winter bag when summer is coming up,
and of course the quality of the make:
1. inside lining, if it's cheap i guarentee i will break it in a month and lose threads will be coming off it..
2. zippers have to be smooth, i always tend to break the zipper too.. hehe
3. i love compartments =) the more the merrier, i like to get organised!

and once i fall in love with a bag.. it's pretty serious haha