Weekends and school holidays should be avoided. Most of the visitors at these times are local people who live in the area, and it becomes very crowded, with very long lines. The park is closed on Thanksgiving and Christmas, so don’t plan a visit during those times.
Visit the Universal Studios website to find out which movies are in production, or which movies will be in production at the time of your visit. This may play in the decision as to when to visit. If you visit during the time of a movie production, you are likely to see the movie set, and you may even get the opportunity to see the stars in action!
When you do visit, plan to arrive well before the gates open. You should arrive at least thirty minutes in advance. You should buy your tickets in advance for added convenience. This can be done through a travel agent, over the phone, or online. Tickets can even be printed out using your printer.