If you don't use Spotlight too much (or don't use it at all) you may want to hide it to free up some space in the menu bar, something that I personally would not do but that you are obviously within your right to do.
You have to follow the following steps:
- Open Terminal.
- Enter the following command: "sudo chmod 600 /System/Library/CoreServices/Search.bundle/Contents/MacOS/Search"
- Enter this other command: "killall SystemUIServer"
- And that's it!
Be careful, this trick does not disable Spotlight, it only hides the icon.
Source | OS X Daily