If you're just wanting to make a large video into shorter scenes, you'll be better off using a program like Scenalyzer, which does it automatically.
There are several methods for accomplishing this, and Steve's recommendation for SceneAlyzer is a good one, if one wants the longer Source File broken into "scenes."
When creating "sub-clips" * one must consider Handles, as if they edit too tightly, and then use those "sub-clips" in a Project, and apply Transitions, Handles will be necessary. This article goes into Handles in more detail: http://forums.adobe.com/thread/701768?tstart=60
Also, using a CODEC, that does either light compression, or lossless compression, will pay quality dividends, when one goes to edit those "sub-clips." This article goes into more detail, for some lossless CODEC's: http://forums.adobe.com/thread/875797?tstart=0
* The term "sub-clips" is used here to denote shortened and edited Clips from a larger "master clip." Note: in Premiere Pro, and some other NLE (Non Linear Editor) programs, there is an official term Sub-Clips, that have a slightly different meaning, and function, within a Project. Similar, but different. Here, I am using the term in a slightly different fashion, hence the " marks, and lack of capitalization.