You will need a park-to-park ticket since Hogsmeade is at Islands of Adventure and Diagon Alley is at Universal Studios & you can ride the Hogwarts Express between the two parks!
Meet the goblins of Gringotts! Look for Gringotts in Diagon Alley where you can exchange your Muggle money for Gringotts bank notes and use them throughout the parks.
Ride the “Forbidden Journey,” located in Hogwarts, & the “Escape From Gringotts” in Diagon Alley which is a mix of an indoor roller coaster & a 3-D ride!
Little kids can ride the "Flight of the Hippogriff" in Hogsmeade. Also try the adult coaster "Hagrid’s Magical Creatures Motorbike Adventure" in the same area of the park.
Visit Weasleys Wizard Wheezes, Madame Malkin's robe shop, and Ollivander's wand shop! Stop at Honeydukes to try the Every Flavor Beans & pick up a chocolate frog.
It is not just for kids! If you're going to Ollivander's, buy an interactive wand and pay attention to details around you so you can get in on the magical fun.
There's one restaurant in each Harry Potter park. You'll find the Leaky Cauldron in Diagon Alley and the Three Broomsticks (and attached Hog's Head Pub) in Hogsmeade!
Don't forget to try a Green Fishy Ale from The Hopping Pot in Diagon Alley! Drink a lot of butterbeer and pumpkin juice. Plus enjoy live shows throughout the park!