Advertising legend David Ogilvy said “Give me the freedom of a tight brief.” A brief that is too vague or general leaves too much to the imagination of the designer. Ambiguous statements are hard to follow. Creative minds work best under constraint. Coffee is best served constrained in a mug or cup.

You need to know what you want. If you don’t know what you want how on earth will the designer be able to deliver? And you can’t say, “I’ll know it when I see it.” What will happen is you will know what you don’t want when you see it. If you take this approach the road to getting what you want will be a bit like Alice’s walk in Wonderland:

“Would you tell me, please, which way I ought to go from here?”
“That depends a good deal on where you want to get to,” said the Cat.
“I don’t much care where—” said Alice.
“Then it doesn’t matter which way you go,” said the Cat.
“—so long as I get somewhere,” Alice added as an explanation.
“Oh, you’re sure to do that,” said the Cat, “if you only walk long enough.”

Too much freedom and not enough boundaries leads to confusion and lost time. I am not so sure you have the time to “walk long enough” to find that magic logo.