As a business owner, the last thing you want to waste time doing is choosing the right furniture. After all, you're the owner, aren't you? Why should you have to waste your time with that garbage? Your job is to wander around your bar or restaurant and tell people you're the owner.
First off, you need to know how much you have available to spend. For instance, if you're opening up a larger restaurant with more seating, you're going to need a larger budget. You might also have to scrimp on quality, in order for you to fill properly seat your dining hall. Take into consideration that extras like upholstery, finishes and whatever brand you've chosen for your business will all empty your pockets faster.
Also, you're going to make sure that the style of furniture you choose matches with the theme of your restaurant. You don't want green tables and yellow chairs unless you're going for some wacky Brazilian soccer theme. Keep in mind that you want to keep this furniture for a long time, so pick something that has a lasting quality. Of course, this should have been done in the beginning stages of the restaurant design, but better late than never!
Next in line is durability / stability of your furniture. This touches on what I mentioned earlier about being with this furniture for a long time. Unless you have some black market furniture connection that will let you empty your inventory frequently (in which case it seems like we'd be in the furniture SELLING industry instead …), then go with something that you feel will last a long time .
A good rule of thumb to follow is that if it looks like it would survive a nuclear attack, add it to your restaurant (food and hostesses excluded!).
Related to this point is what your furniture will be made of. Most commercial goods are a mix of plastic, metal and wood. While wood seems to be the most popular style of furniture, plastic is the cheapest and most flexible with regard to design. Metal has better heat resistance and mechanical abuse, but unless you expect Iceman or the fiery guy from Fantastic Four to eat at your establishment, you probably won't need the metal.
Go with plastic!
Finally, make sure you buy from a supplier which offers a warranty. In general, I would advise against making expensive purchases without a warranty agreement in place. Its no different in this case, as the last thing you want is to drop $ 15k on some termite invested furniture, only to have no legal recourse when your chairs and tables fall apart in the middle of the lunch rush.