Lightning Lanes allow you to skip the standby line and enter through the Lightning Lane (previously called Genie+ or Fastpass line). The wait time for the Lightning Lane is usually 10 minutes or less. If the ride you are doing has a wait time of 60+ minutes, this is a huge time saver. If your budget allows, I would suggest getting the Lightning Lane Multipass for, at the very least, Magic Kingdom and Hollywood Studios. I do not think it is absolutely necessary for Animal Kingdom or Epcot unless you are limited on time or visiting during a high crowd period. I send a personal guide to all my clients. If you use this to plan ahead, you should be able to book 5-10 rides with the Lightning Lane Multipass.
WHEN TO BOOK
The first thing you need to understand is when you're eligible to purchase Lightning Lane Multi Pass. Everyone can purchase Lightning Lane Multi Pass on the day of their Walt Disney World visit, but you’ll want to take advantage of pre-arrival windows to ensure you get the best selections.
Staying at a Disney Resort: 7 days before check-in
Staying off-site: 3 days before your ticket start date
Both of these will be eligible to purchase at 7am EST
KALIE'S TIPS
Try to schedule your advance selections for the morning so you have more opportunities to book rides later in the day (this will be easier to do on park days that are towards the end of your trip).
The app will allow you to overlap times by 20 minutes. Take advantage of this, it will allow you to get more done. Most of the time, you won't have to really worry about selecting times because the system will automatically book the first and best available return time for each attraction, with a decent buffer between them so that you’re not double-booked. However, this default will be no overlap at all, so if you do want this 20 minute overlap, make sure you go in and modify before checking out.
While in the park, as soon as you tap in to your first advance selection, go back into the MDE app to choose another (you can hold 3 at once). You will keep doing this as long as there is availability. This is why it's important to select rides in the morning. If you do three rides, for example, 9:00- 10:00, 9:40-10:40, and 10:20- 11:20, you could get a 4th, 5th, and 6th ride all booked by 10:20. This is the absolute best way to maximize the value of the lightning lane multi-pass.
If you have a park-hopper ticket, you can only choose advance selections for the park you will enter first, however, your next selections can be in any park. Again, it's best to book these early so you can immediately get one for a high priority ride in another park.
Highest priority rides in each park are: Tiana's Bayou Adventure in Magic Kingdom, Slinky Dog Dash in Hollywood Studios, and Remy's Ratatouille Adventure in Epcot.
Seven Dwarfs Mine Train (single LL pass or stand-by)
Tron (single LL pass or stand-by)
Guardians of the Galaxy (single LL pass or stand-by)
Rise of the Resistance (single LL pass or stand-by)
Avatar Flight of Passage (single LL pass or stand-by)