Most users know that you can easily create .zip files in OS X by selecting a file in Finder and choosing File » Compress "FileNameHere" or by control+clicking the file and choosing the same option from the context menu. You can open .zip (and other archive formats such as gzip, tar, and bzip2) simply by double clicking on them.
You may not have known that additional options are available. For example, after you make a .zip file, you could have the original files moved to the trash automatically, or you could have all .zip files that you create automatically saved to the same folder.
Similarly, you can have all archive files that you expand open to the same directory as the archive, or have them saved to a specific folder.
The feature that I was looking for was this: after I expand an archive, just move the original file to the trash so I don't have to, because I don't want to keep it.
If the default settings work for you, great! But if you'd like a bit more control, there are two ways to do it. (Note: these system paths are current for Snow Leopard. Previous versions of Mac OS X may be different. See note at bottom of this message.)