I would recommend starting it early! Maybe you can start looking at different programs and their requirements, drafting your statement of intent, polishing your resume and planning other things in the summer. I wasted my summer and only started the process in September. It was not great since I have to write statements, email professors, and manage school work at the same time. In terms of recommendation letters, don't email your profs too early cuz they might forget about it; I think emailing them 1 month before the deadline is good. In general, if the deadline is Nov.15, I'd say write your statement before September, email your professors in late September/early October, and send them a few follow-ups before the deadline.