Your chances of getting a ballot place may be limited. This year they extended the ballot to lasting a week, and approx. a quarter of a million applied (the race limit is around 38,000). Results of the ballot usually come out the beginning of October.
You don't have to be a member of a running club, but it may offer you a slightly better chance of getting a place, especially if it is a club like the one I'm a member of that provides volunteers for the event, as they will be offered a few additional places.