Conceptual design - The creative process
A few months ago, I wrote about how different designers have different strengths and weaknesses and how you can map their skills on a notional prism. Your skills may be in illustration, or typography, or in lateral thinking - it takes all sorts. The chances are, that you have been chosen for a particular design job because the client likes your previous work. They probably want you to communicate a message about their product or service in your particular style. That's a good start.
No matter how good your design looks, if it doesn't communicate the required message, it isn't doing it's job - nor are you. Style is something that complements or embellishes an idea, it doesn't supplant it.