I prefer e-mail as the method of communication, but can provide phone contact information in some cases.
I like to get as much information from the client as possible before proceeding with a project. I have a questionnaire available for more complex projects that helps in the start of the process to insure that the client gets what they are looking for from the start.
I work as a full-time freelancer, but am up front when I won't be available to work on something. This does include working some weekends. I try to be realistic in deadlines and am available to answer questions via e-mail, even after a project is complete at no additional charge.
I appreciate feedback once a project is complete and do the same for all my employers.