This is a video by Indy Mogul. For making a script or screenplay, first write a short heading about the situation and where the characters are to be at that time. Then write the actions the character must do. Then the dialog the actor must tell along with the emotion. Now write the dialog the another actor must say. Like wise write all the dialogs. Time must be ascertained for each dialogs. Dialogs must be written according to the time.
There must be some ideas in your mind for writing the script and make your mind running. You can also see some movies like silent movies, music, etc. This will help you to make your script more powerful and beautiful.
This video will help you to learn how to make a script or screenplay.