Watch the movie in its entirety and look at each scene critically. If some do not move the plot forward or are just unnecessary, cut them out of the movie entirely.
Place the title and credits over a video clip instead of their own slide. For example, instead of listing all the participants at the beginning, start the movie and have the names overlay on top, with the title.
Don't show any "traveling time." Viewers will understand how characters get from point A to point B without showing the actual traveling. Cut out any unnecessary explanatory shots.
Avoid using fancy transitions between clips. Use quick transitions where you can, and save the fancy ones for the beginning or end of the movie.
Ask another person to view the movie to see if there are any unnecessary or drawn-out parts that could be cut. Choose someone who has never seen the film or heard the script before.
Consider re-shooting certain scenes if they are too long. Sometimes a re-shoot is necessary if you decide to make changes in the post-production stage. However, re-shooting scenes depends on time constraints and budget and is not always possible.