I like a peaceful atmosphere, big squashy sofas, the fact that in Starbucks you can sit round the corner with your laptop and a drink and not get disturbed.... QUIET music, if any, so you can still talk! Local artists' paintings on the wall for sale... you could make it a gallery too and hold the private views in the cafe...
Also, make it into a place where acoustic music can be performed. Maybe just 2 musicians at al time and no amps- just singing and guitars etc.. People LOVE that sort of unplugged live music! You could do your own unplugged night every week where members of the audience can get up and sing etc. Not nasty karaoke, but something a bit different.
For food, I would go for Cranks-style. Homemade as well as bought in cakes and verging on the veggie- wholefood type of hot food, Paninis, posh stuff, but not too expensive. People always come back if they get a decent portion of NICE food too!
You should make the interior classy- maybe whitewashed with water/pebbles/bamboo, spotlights and ultra-violet hanging lights/fairy lights. Aim it as a sanctuary for students too, as they have disposable income, hours to spend during the day drinking coffee and they will bring all their mates!!