It is really best to allow six months ahead for planning big events like weddings. WHile it is always important to think ahead, there are two very important reasons why this is so:
For one, lots of people have things that they like to do in the summer. Many plan all year for a little bit of time that they can have together when it gets warmer, here in Upstate New York. Therefore, if you want a good turn out, you need to give your huests plenty of time to make sure your wedding will be a priority.
The other reason is vendor availability. Coordinating the three important facets to your wedding's success is crutial. The hall/cateror, the disc jockey or band, and/or any sort of photographer & videographer, are often booked up sometimes in upwards to a year in advance. This means if you have someone in mind for each of these roles, you have to give yourself plenty of advance time to make sure that they will be available. Also, keep in mind, the real good vendors book up even faster.
If you follow these ideas, everything will turn out great! Good luck!