When you do an initial "Save" of a new file, you are prompted to type a filename.
But if you already have a file with the name that you want on your hard drive or server, you can just click on that file name in the File > Save dialog box, and the name of the file you click on will be entered as the filename. Then you can edit the filename if you don't want to overwrite the original file.
This is a pretty basic operating system maneuver that works on both Mac and Windows computers. I showed this to a client last week, and they were so amazed and grateful, I thought I would post it here in case others don't know about it.