Spotlight
Spotlight is a fantastic tool. But sometimes it needs a little maintenance to keep it in shape. Here's an option in Yosemite that might help keep Spotlight humming along as a perky little helpful utility.
As we saw earlier this year at WWDC, Yosemite has a wider variety of sources from which to gather search results. Not just files on your internal or external drives, but all kinds of other places too. Now you can also get results from websites, Maps, iTunes, and more. While that sounds awesome to some, to other people it's overload, and that's not to mention when your connection isn't the greatest, Spotlight is even slower.
So here's how to trim down those sources in Spotlight. First, go to System Preferences > Spotlight, and uncheck things you don't care about:
System Preferences for Spotlight. Uncheck with impunity.
Now if you truly wish to level up, think about all the things you search for using Spotlight. Is it mostly a way to locate an email, or perhaps a PDF? Maybe a particular folder or just spreadsheets? That list above is fully adjustable; just click and hold on a Spotlight category and adjust them at your leisure to rejigger the order in which you see results. If you mostly need email, put it at the top, and so on. So far this is one of my favorite tweaks in Yosemite, so I hope it gets more attention. Tell your friends!