Those exchanges do ask for KYC nowadays after the governments crackdown on money laundering and now people have had to move to other instant exchanges for quick conversion from one coin to another. At one time shapeshift was the most popular one used.

Of course the few things that one looks into have been said by other members, of which I will point out the ones I like:
1. No KYC would be best, but maybe that is no longer possible.
2. A quick response support team active 24x7
3. Responsive UI on both web and mobile, maybe a mobile app too, but is secondary for starters.
4. Discounts for loyal users.