The best way to explain something is to respond to your audience's reactions; if they are lost, either decide that point isn't important and get to the implications of it or try another tact. Responding to their reception makes your audience felt heard and validated as well as making it more likely they will actually understand what you are saying. It takes skill and practice, but when done well the difference is staggering.
What you should be sure of is the underlying, abstract thing you are describing. You should know the story is "Snow White", even though this time the audience might not care about dwarves and might not be laughing at the funny squirrel bits, but is really interested in glass coffin construction. If you know your idea inside and out, it is easier to find the part of it that this audience right here is interested in, and you know what the important parts are that make the rest of it make sense. Ideally, you shouldn't have to plan answers ahead of time, because the answers are obvious.
The less superficially you know your idea, the less work presentations are to put together.
What you should be sure of is the underlying, abstract thing you are describing. You should know the story is "Snow White", even though this time the audience might not care about dwarves and might not be laughing at the funny squirrel bits, but is really interested in glass coffin construction. If you know your idea inside and out, it is easier to find the part of it that this audience right here is interested in, and you know what the important parts are that make the rest of it make sense. Ideally, you shouldn't have to plan answers ahead of time, because the answers are obvious.
The less superficially you know your idea, the less work presentations are to put together.