Preview the movie and take notes. Earmark key points that you want your students to look for as they watch.
Create a lesson plan. Make a daily schedule calculating how many class periods it will take to show the entire piece. Organize viewing time into segments. Leave time for you to introduce the movie on the first day, and summarize each consecutive day until the movie is completed.
Prepare your students for what they will see. Tell them to be on the alert for certain elements that they should be looking for. For instance, if your movie depicts the Civil War and you are studying Civil War generals, have your students identify the different generals when they see them. Conclude each day with some targeted questions to draw out the main points that they need to understand.
Instruct your class on proper behavior for watching the movie. This is not watching TV at home. If they blurt out their own thoughts, it will disrupt others. Give them a quiet signal they can use to say "I found it." For example, when they see a Civil War general on the screen, have them raise their hand with one finger up when they first see him.
Sum up the event with review. Ask questions of the group and give them a class assignment to reinforce what they have learned. Whether it is a project for small groups, making a poster to display, or a worksheet, your students will benefit most from a recap of the information soon after it is viewed.