Actors have an incredibly good memory for lines of dialogue, but they typically don't use complex mnemonic techniques to remember lines. In fact, author Annie Murphy Paul notes in Time Magazine that in most cases, it's as simple as tying the words to an action.
Image: Barry Solow.
The idea is that when we tie the words we're trying to remember to an action, it settles into our brain a bit deeper. Paul notes:
Words are often intimately connected to actions onstage. Cast members' movements are carefully blocked out during rehearsal and so their lines are always matched to the same physical motions, forming a kind of bodily mneumonic device.
Of course, we're not all actors and don't need to remember thousands of lines of dialogue, but if you're gearing up to give a speech or presentation, this technique could come in handy. You don't have to over emphasise every movement you make, but by paying attention to the gestures while practicing your presentation will help embed those words in your memory. The same could even be said for your posture or handshake when you meet new people. Note your own actions along with the person's name and it can help embed the name in your memory.
What Actors Can Teach Us About Memory and Learning [Time Magazine]