1 - Leather soles are a must! First they epitomize quality and superior craftsmanship. Plus they soften with age.
2 - They need to have a bit of pizazz, whether it be pattern, colour or a buckle your shoes deserve to be accessorized.
3 - Make sure they fit, leather stretches with use and personally I cannot stand sloppy shoes. Make sure you buy your shoes snug. They should not pinch but your heels should not slip.
J.Crew has updated their classic flats with softer soles and padded insoles. At $146 CAD they are a steal.
Repetto, known for making ballet shoes for over a century they recently began making ballet flats. Their shoes are made just like their ballet slippers and offer unsurpassed comfort and elegance. I will warn you they cost a pretty penny, about $250 CAD but if you can wait, save up and next time you are in Europe you can snatch them up for 150 Euro. The black are of course classic but the nude patent ones are on my wish list.
When I think classic, Kate Spade always comes to mind. This Spring these adorable jelly flats will make your friends green with envy. Did I mention they are only $95!