Ask your doctor. Doctors go to theme parks, such as Disneyland, for medical conventions. The pharmaceutical companies put these events on and then give the doctors extra tickets for their family. Many doctors are too busy and receive too many tickets. Ask your favorite doctor if he has any.
Visit one of the roadside discount ticket offices. The highways along the East Coast are littered with signs for discount tickets.
Go to fast-food restaurants. Many fast-food restaurants near theme parks do a marketing campaign with the theme parks in the popular months.
Check your local grocery store. Many of the grocery stores have discount tickets to local theme parks.
Ask the theme park if they have special discount days. Many theme parks have a "bring a friend" day. The friend is usually discounted, so all you need to do is find a friend to take you.
Inquire at your school or homeschool group if they know of any discount tickets. Many theme parks have education days. The tickets usually have to be purchased through the school and in advance.
Check inside an "Entertainment" book (see Resources below). These books costs about $20 and have discount tickets for many entertainment venues, from dining to theme parks.