Your workspace should provide enough space for everyone you employ, in an environment with no distractions and comfortable seating.
Dedicated desks for your staff let them have a spot to call on their own - free from the 'first come first serve' chaos of sharing tables.
Having private areas is just as important in coworking spaces, as they are great for sensitive meetings as well as providing a quiet place to escape and re-energize. Conference rooms with blinds and locks are the perfect way to ensure privacy when needed.
While amenities are far easier to deal with than the preceding attributes, they also take some of the pressure off.
Some coworking spaces offer a canteen or kitchen where customers can purchase food. Others merely offer vending machines and coffee makers.
The coworking space's amenities are even more crucial if the location you select is far from any restaurants or convenience stores.
The availability of amenities eases some people's concerns that they won't have time to prepare their meals.
What specifics about upcoming activities in the coworking space? Are there any dedicated areas for business gatherings or networking conferences? Do they organize events, or can you use the space for your own? Since these activities aren't strictly related to work, it's something to think about. It'll also help you anticipate how "busy" a day might be if they have a special event going on.