Go on Tuesday and Wednesday
Generally, Spring breakers want to zip into the park the first day they don't have class, which is often a weekend or a Monday. Days to avoid in the park are Mondays, Fridays, and weekends. This tends to be when families will also be in the park because it's easier to get a day before or after the weekend off. If you want the park at its least crowded, Tuesdays through Thursdays are your best bet. Also, you need to decide how long you want to be in the parks! If you're doing a day trip, either invest in a park hopper and the MaxPass app (which is an extra $10) or choose to do a single park pass. No matter what, you'll want to get to the park right when it opens for the shortest lines.