For day-hiking (except Mt Whitney) you do not need a permit.
If you plan to hike and stay over at least 1 night, you need a backcountry permit.
If you cannot reserve one ahead of time at Recreation.gov, then you will be trying to obtain a walk-up permit. Most people are looking to reserve an “Overnight- Not Exiting Whitney” permit. Unless you plan on using some major map and compass skills, you will not be applying for a cross-country permit.
You are only allowed to get your permit 24 hours in advance of your planned start date. Following the below steps will help you navigate this process.
Before you even go to the permitting office:
Make an itinerary for a plan A, B, & C with your maps and using the Recreation.gov site for trailhead names.
Know the trailheads that you want to start from and approximate areas you want to camp each night.
Day of going to office:
There are 4 locations that serve that area:
Eastern Sierra InterAgency Visitor Center
Mono Basin Scenic Area Visitor Center
White Mountain Ranger Station
Mammoth Lakes Welcome Center
Arrive at least 1 hour ahead of opening time to get in line. Most open at 8am, so be in line by 7am.
Once the doors open, you will one at a time go up to a signup sheet to write the trailhead you want to start from and your name.
You can then leave to go get some breakfast and a shower.
Be back no later than 11am. They will start calling names according to the list at that time.
They will start with your plan A and then work from there. Most trailheads have around 40% of the allotted permits held out for walk-ups, so if you are in the front part of the line, you have good odds of getting the permit you want.
Remember all of the Leave No Trace principles as they will ask you questions about them in order to get your permit.
Have your California Campfire Permit all done and ready as well. Even though you cannot have campfires in most areas, you still have to have one to use a cook stove. They may ask you about those rules too.
Know your car make, model, and license plate.
After that, you are all set. Get your gear all packed up and get a good night’s sleep.