As a California native, Disneyland is genuinely in my blood. I have been more times than I can count, and I know how to make the most of a single day in the park. If you only have one day, here is how I would spend it.
Arrive before rope drop
Get to the park at least 30 minutes before opening. The first hour of the day is your best chance to ride popular attractions with short waits, so do not waste it grabbing coffee inside the gates. Eat breakfast before you arrive if you can.
Head straight for your top priority ride
Whatever your family's must-do attraction is, ride it first. Crowds build quickly, and the ride that has a five minute wait at rope drop can have an hour wait by mid-morning.
Use Lightning Lane Multi Pass if it fits your budget
I will be honest, it is expensive. But it completely changes how you spend your day. Instead of standing in lines, you are riding more and enjoying more. If a specific ride is a must-do for your family, keep an eye out for Lightning Lane Single Pass too, which lets you skip the line on select high demand attractions for an extra cost. If you decide to use either one, get familiar with how it works before you arrive so you are not learning the system on the fly.
Mid-morning: work through nearby attractions
Once your top priority ride is done, work through other attractions in the same area of the park before moving on. This cuts down on unnecessary walking back and forth.
Lunch: sit down and breathe
If you have time in your day, I always recommend one table service lunch. My favorite is Cafe Orleans, though The Blue Bayou is unmatched for ambience if you want to sit creekside in the dark while the Pirates of the Caribbean boats float by.
Early afternoon: save time for a park hop
If your ticket includes park hopping, early to mid-afternoon is a good window to head over to California Adventure for a few hours before returning to Disneyland for the evening.
Grab your must-try snacks along the way
A few of my personal favorites: churros from the carts, the raspberry macaron, which sells out every single day so grab it early for pickup later, the corn dog from Corn Dog Castle in California Adventure, and the cheesy garlic bread pretzel.
Evening: save energy for nighttime entertainment
Fireworks and nighttime shows are some of the best parts of the day. Find your viewing spot early if it is a popular show, and save a little energy so you are not too worn out to enjoy it.
Plan for the temperature drop
Disneyland is warm during the day, but it gets chilly once the sun goes down. There are lockers near the end of Main Street if you want to store a jacket, though my personal strategy is just buying a sweatshirt in the park in the evening. It is part of the experience.
One day is possible, but it takes planning
A single day at Disneyland can absolutely work, especially for couples or families with older kids. If you have young children, I generally recommend spreading your visit over two or three days so no one feels rushed.