Here is the best and easiest way to memorize lines as an actor.
The easiest way to learn lines for a movie or TV show is to record all the lines and play them back and sa them along with the recording. You can record with your computer, phone, or even a recorder. However, it is very important to hear the cue (the line before yours) so you know when to say your line. Play it over and over and say your lines along with the recording. Then when you know it better, pause the recording after the cue line and say try to say your line. Listen to that line and see if you memorized it right and then try again.
Another way people learn lines including reading the script and covering your lines up. Here’s how you can do it. Read the cue line and then try to say your line while it is covered up. This works even better when you are working with a partner. Another unique way to memorize your lines include looking at the cue line and then trying to type your lines without looking at the script.
At the end of the day, Everyone memorizes differently so it is good to try different techniques to see what works best.
But, the best thing you can do before you head on set is to do a speed through with the other actors. Sit or stand together and go through the lines as quickly as possible. Have someone mark down the lines you miss and read them over and over before you go on.