The more the description of the desired object in the picture is better. Even if the description of the client will appear strange or silly it is better than too abstract objectless explanation.
When somebody comes to me and says he wants to warm sweet tattoo - it could be anything.I have such an explanation will cause one association and another person to another. And I will draw a sketch of which as a result will not be so that the client expected. Because at the words "sweet and warm tattoo" I will represent as an object of the lamp, and the person will be the object pillow) as very simplified example. )
So I ask people who want to tattoo to explain it as detailed as possible - then the figure will be made easier.
There are certainly exceptions, when prepared by drawing directly suited to the client, even though he had little to explain what he wants. But most people come in and ask for "something beautiful no matter what"=)