1. Start by reading the play a few times. The first time you read should be to get a general overview. The next few times should be for picking up details you may have missed and getting a deeper understanding of characters.
2. Make notecards of your lines. Write the cue line on the front and your line on the back. Now you'll have cards to carry with you everywhere! You can also make them using a flashcard app on your phone, but I prefer writing them out.
3. Run lines often with friends, family, and pretty much anyone who is willing to help.
4. Review lines right before going to bed.
5. Highlight your lines in a color you like.
6. Don't stop reviewing your lines just because you think you're off book. Review often to keep the material fresh in your mind.