Marketing is the unsung part of theatre. While the glamour and applause go to the cast and crew of a play, selling the play starts month earlier. The bigger the volunteer army you can unleash to market and talk up your play the better. It is much easier to market a big cast show like a musical than it is a one man show. The math is obvious. Many people have more friends than one person. Actors cast in plays for the first time will generally bring more people to the show than will seasoned vets. Stick a six year old in a play and every relative from miles around will come to the show. For the intents of this article there is paid marketing(advertizing) and unpaid marketing(promotions).
As the old adage goes, you need to put bums in the seats. The equally age-old question is how do you do that?
Inviting socially important people to opening night, in fact filling the house with freebies works as a great word-of-mouth push. Generally trays of food and wine are further inducements. If these freebies have an enjoyable night out, then they will talk the show up. However it also works in reverse. If the show is not worth talking about it might wreck any future audience numbers.
Impress upon the cast and crew that they have to talk up the show. They are your main marketing tool. If they don't feel passionate about the show then no one else will. For marketing purposes in a local production, I can't think of a more valuable marketing tool then the folks that work on the show. With a big show, it is like having a huge sales force working for free. They need to be motivated. It is sometimes difficult for actors to promote themselves. They have their insecurities. But of the actors that succeed in climbing the ladder in live theatre, most are good at promoting themselves and hence the shows that they are in. It all comes down to getting bums in the seats.