Making sure you understand your skills and understand how to plan.  Understanding your skills helps with establishing goals and objectives for your clients for the duration of your projects.  Planning and projecting is key to establishing points of reference for you and your client and is a measuring device that can determine how well a project is doing.  In the end communication is very important, letting your clients know what you are doing, where you are in the process, if there needs to be any adjustments, and when they can expect closure for you services.