Make sure that planning is done way in advance, cramming is not the best way to prepare for a birthday party. Inviting your guests early can give them time to prepare and free up their schedule.
During the planning stage, hiring a reliable birthday planner, E Magical Moment for example, can help you big time achieving success.
Anyway, birthdays do not come as a surprise, hence planning months in advance is possible. Two, three or more depending on the size of the event is recommended.