I go to files, create a new folder with the project name, move the group of files to that folder, then delete the non-video files. I change the file names to large icons, so it is easy to tell the video clips from the non-essential files that always come along with them. I review the clips from the folder, not from the stick, and rename them with subject and good/bad so they are easy to use when assembling a video. Then I go to that folder when I "add a clip" from the Moviemaker program. I keep still photos in a separate folder from the videos. It is just a matter of having a system and practicing.
I do not clear the stick until I remove it to put back in the camera for the next session.