If I was the new Director of Marketing for the Boston Celtics I would first look at the price of the tickets. I would see if the price of the tickets were reasonable for the public. Figuring out whether or not the ticket prices were too high based on how desirable going to a Celtics game is for the average person would tell me if lowering prices was essential to benefiting sales. Possibly lowering ticket prices even if it's only by a little bit might result in an increase in sales. Selling more for less is better then selling none at all. The price of going to a Celtics game must entertain the public cheaply and moderately with respect to the price the general public would be willing to pay to see a game.
Another aspect I would take into consideration would be the product itself. Tickets to the Celtics games must be desirable to the consumer. You need to have the consumer want the product. If the Celtics aren't having the best seasons this will by far affect the sales in a negative way. I would try to make the product better by having specials at the game. One way of making the game more desirable could be giving a certain number of souvenirs away to the people that attend the game. This might make coming to the game more exciting for the ticket holder. This could cause them to come to games more frequently which will trigger a chain effect for more people to buy tickets. For example, If Johnny got a free Celtics tee shirt and goes to school the following Monday and tells 10 of his friends that he got a free Celtics shirt this could possibly result in more families attending which would raise ticket sales. .
One idea to raise ticket sales could be to focus on season ticket holders. Possibly increasing incentives for season ticket holders could generate a more positive effect on season ticket holders. A type of point system could be created for season ticket holders by giving a certain number of points to a season ticket card when they attend a game.