When I first meet with a new customer, I want to know what they want done first.  Once I have that information, I can begin to prioritize the tasks to complete that project.  I may also ask for an overview of the business, so that I understand what the tasks are that I will be asked to work on.  
Just as with any business organizing or office management task, the first project will set the tone for projects or additional work that may follow.  Once I understand the management "style" of the business owner, I can work on the project or projects accordingly.  Then, it is up to me to arrange my work schedule to accomplish what needs to be done in good order.  Once the project/projects are underway, then I can pause, if necessary, to push another project to the head of the list, due to urgency.  If I know in advance, I can put projects on a calendar to assure that they get done even if they are days in the future.  Being able to flex with the client's needs and rearrange projects will help me assist the client in managing his/her business effectively.  Knowing the priorities and working on them accordingly is one of the things that I can do to make sure the client's needs are met.  Getting feedback by asking questions during the course of the project is another way that I make sure the client is getting what he/she wants from my services.  Meeting the client's needs is always a prime objective of the way I work to assure that the client is happy with the end result.