It is vital that you plan ahead for the whole process of writing your dissertation, from beginning to end. This is particularly important for a Year Abroad Dissertation, if there are periods during the year when you cannot work on your dissertation. But it is also important for the Optional Dissertation, as you will need to juggle your dissertation work with the demands of your other papers, which may vary at different points in the year.
The links below take you to some suggested work schedules. In every case it is vital to agree a schedule with your supervisor, in case he or she is unavailable for particular periods during the year.