It is you that tells the agent what to search for. And you are right, in most cases the agent may not know what to look for, so it will be up to you do explain. A lot also depends on the type of business you want to operate. Things will be different for a sit down vs a drive thru. The only 3 things the two will have in common is (yes you know what I'm going to say) LOCATION...LOCATION...LOCATION. So when considering where you would like for your place to be, keep those things in mind. It is never a bad idea to have as many contacts looking for locations as possible. The more you have looking, the better. Sometimes you may have friends, relatives or co-workers find a location before an agent. Remember you have to pay an agent for their services, but not necessarily your friends or relatives.
If you select an agent don't be concerned about how pushy that person may or may not be, it is the nature of their job, that's how they earn their commission. Also look for any business brokers that may have a few businesses to show. Another thing you can do is search the business opportunities section in your local newspaper. There are usually a few listed there. Anyway, just a few thoughts... 8)
agents are a great source of information about an area or neighborhood but filter because they are sales people. do your own research and compare all info so you can make the most informed descion. As I am walking around an area the thing I look for are for rent signs by owners, even though I get info from an agent I tend to rent directly from an owner.