By posting a certain number of tickets and / or for a certain period of time, you create a buzz. Make sure the discount is a good one, especially if it's a long time in advance. Earlybird tickets gives you cash flow well in advance of the event, gives you confidence and a hint of the interest, and not least, those who buy early will be good ambassadors for others. They will recruit new buyers for you - everyone wants to go to a concert , festival, standup, conference, trade fair etc. along with someone else.