Off the top of my head:
1. Music
Play a wide variety of interesting genres and know exactly WHEN to play them. For example, early in the day you could rock downtempo, acid jazz, triphop, soul at comfortable listening levels. At night after diner you can add some BPMs to get the place hopping.
2. Lighting
My biggest pet peeve are places with terrible lighting. (Think hospitals, government offices and other misc places of misery.) Use warm, natural lighting, preferably with a dimmer for more control. Also, indirect light makes people look better, so think wall sconces and fixtures that illuminate of walls and ceiling instead of shining in people's faces.
3. Amazing Coffee
First step would be to get a decent espresso machine.. they are a bit pricey, but a good one will last you decades. Experiment with different blends to find a unique signature flavor. Me, I like a blend of Kenyan, Cuban and Columbian coffees.
4. Decor
It's good to be stylish, but some places are overkill. A great cafe almost feels like an extension of your house. Maybe it has some modern/designer touches, but the overall feel is homey - sofas, easy chairs, etc. It should be inviting.
5. Terrace
Huge bonus would be some tables and chairs on the street or in a garden to enjoy some outdoor vibes.
6. Service by hot chicks
^^ No explanation needed
