spotlight
Since spotlight continuously updates the index, sometime the file precedence gets changed around and I might type in "saf" and press return expecting to get Safari, but instead spotlight attempts to open some Java jar file.
Question Is there any way to make spotlight ignore certain file types or directories?
On the root of each indexed volume, a hidden folder called .Spotlight-V100.
Also: spotlight metadata is probably not large enough to be worthwhile in excluding, at least if you are doing this for space reasons. Spotlight is also essential for TM to work properly, as this is how TM determines which files have changed since the last backup.
I'm not aware of a solution in Spotlight with(-out) tinkering.
It certainly would add a lot of "trouble" to users with HDD as the the amount of file to index will be too much - hey, after all it's the / directory...
Quicksilver allows to index user defined directories in Preferences → Catalog. You can then define the dept to which you want to descend. Optionally, you can even descend in bundles!
Best Answer
Short answer: yes.
Go to your System Preferences, then Spotlight:
You can disable and/or reorder the items in this list. By dragging Applications to the top, "Saf" will match Safari first (because it's an App, regardless of it's location).
If, on the other hand, there's a Folder(s) or Drive(s) that you want to explicitly exclude from Spotlight until you change your mind, turn onto the Privacy Tab (on top of that panel) and click the (+) button to browse for a folder.
This window also accepts Drag and Drop of Folders or Drives (Volumes). In my Sshot, you can see that I exclude Clone (my weekly clone drive) from Spotlight so when I search for something I don't come up with duplicated results (one from the main drive and one from the backup).
I also have added a Public Folder where a lot of ppl drops stuff and I don't care about it nor I want it in my search results.
If you want to restore it, you can always remove it from this list (and give spotlight time to re-index it).
You can't (as far as I know) exclude by File type.
Note: in order to drag a "drive" just go go the finder, click on your Mac OS Volume and then press ⌘↑ (the up arrow) to go back to the "root", you will see your volumes there (among other things). Drag it and drop it onto this Privacy tab and voilá.