Carefully Plan Projects in Advance
By carefully planning out projects in advance, you will show that you are able to take initiative, and that you want to understand the project completely before getting started.
This is true whether your client has provided you with accurate and detailed guidelines, or a vague explanation of what needs to be done. You should establish guidelines as soon as possible, and return them to the client for review; this will allow both of you to see exactly what the work will entail.
How we do it: Every proposal we send out has a deliverables schedule that outlines what is expected from us and from our client. Clear expectations right from the start. This makes my OCD very happy, but even better, it makes our clients feel secure and understand how everything is going to go down. We like some surprises, like when the puppy jumps up on our lap in the middle of a conference call; not when it comes to client expectations though.