I want to take portions of three videos and insert them in various places of the time line. Like a commercial in which different people are saying parts of the same script. What is the best way to do that without ruining the original videos? I had each person record the entire script, but now I want to splice them together.
You can't ruin the originals, because Pr doesn't do anything to the original files. It "imports" media only in the sense that it links to the media on the drive by it's location on the drive.
So there's a number of ways to do what you want ... including selecting all clips, right-click "create multicam" if there's some continuous audio somewhere for Premiere to use to create a full sequence. Like if you've recorded with a separate recorder and they were all talking forth & back at one time.
Or ... make subclips of each segment of a person talking, name the subclip for what they're saying. Drag/drop the subclips in order as you need them.
Or ... make a sequence of each person talking. Then use the Captions workspace, and have Premiere make captions/subtitles. Now you have text with timecode for each clip, you can select bits from the text and add them to your sequence.