For the price-conscious, the best deal is to stand in the long lines at the red-and-white TKTS booths. These booths are easily found in the South Street Sea Port (199 Water Street) and the center of Times Square (47th street at Broadway). TKTS are operated by a non-profitable organization, the Theatre Development Fund, whose purpose is to make cheap theater tickets available to the ordinary theater lover. They generally sub charge $3 per ticket and accept only cash. The main discomforting factor is having to stand in long lines for hours.
For individuals for whom time is not a constraint, opting to be a volunteer usher is the best way to get to see a show completely free. One merely has to be at the theater where the show is staged, about 1-2 hours early, to receive the instructions. Scalpers are an illegal and risky way to get tickets, and are best avoided. Another option, especially for those not close to Broadway, is to opt for online booking, or applying for membership to a Broadway club. One can hope to get discounted rates, occasional free giveaways and subscribed tickets.
Some online options may be a bit expensive, but they are safe and their contacts ensure that one gets tickets to the most popular shows, as well as premium seating. Stand-by tickets are generally given away at cheap rates at the last minute. However, one has to find out in advance if the theater offers such tickets for a particular show being staged.