1 Try to go through your lines while doing something else (I juggle while saying my lines). Maybe get into costume or apply your makeup. The split focus, on the activity as well as remembering your lines, is a good simulation of being on stage; your reflexes are ready and reactive to what's physically around you while your brain takes care of the logic behind the lines.
2 Go through the logic of the argument/dialogue step by step without the lines. Find the flow of the argument.
3 Find the cue word or phrase in the other character's dialogue that makes you want to say your line. This helps you to focus on the other actors and exactly what they say rather than just listening out for your cue.
