you can tell them a main category, and the possible categories that the diretories can have.
If I were you I would give him the basic information and if the one I hire asks me about categories I would tell him to go F..ck himself, I would tell him that he is the one supposed to be telling me. I think that when you hire someone that person should be someone knowledgeable and savvy in that area. i mean its like if I hired someone to do my SEO, and he asked "what keywords do you want me to use?, Which search engines are best to submit to?" I mean hahaha, the moment he asks this you just end all relationship with this person.. the same is if you hired someone to submit to Directories, Article Directories, etc.. the least you can expect them to know is where that link belongs... if you think not, then why are you paying them for? just for typing some url in some place YOU HAD TO TELL HIM TO WRITE???, then you are not looking for someone for directory submitting you are looking for a typist.
in my opinion there are a lot of people that are as lazy as me out there, difference is that I know that if Im lazy at work I wont get paid and in the other hand they still think that they will get paid for being lazy.