Create a plan before your writing weekend. This could be a thorough outline of the content of your book or just a collection of character maps and plot summaries. The more source material you have to draw on when writing your novel, the easier it will be for you to stay focused.
Eliminate distractions that will keep you from your work. You can really only write or type so fast, so time wasted on other tasks will prevent you from completing the task. Television, Internet, friends and family -- these can all be hindrances that will keep you from achieving your goal. If possible, visit a location that will keep you to your writing, such as a remote cabin or a hotel room.
Stock your work space with food and other necessities. You will need to focus your time on writing, so going out to the store to get necessary items or running errands can take you away from your work. Reserve time spent away from your writing over this weekend for inspirational walks and brainstorming sessions.
Start free writing. Whether you already have a concept for your novel or not, some free writing is always an exercise that can help get the juices flowing. This free writing does not necessarily have to be included in your final work, so do not fuss too much over spelling, grammar or even making sense. Once you start free associating ideas, you can narrow in on the intention of your work.
Save editing and revision for the week after. Your work does not have to be a finished product over the course of this weekend; rather it should be a solid first draft. Revising is a careful process that will likely take several attempts until it is complete and the book is ready to submit to a publisher.