Firing up System Preferences and clicking on the Spotlight icon (or clicking on 'Spotlight preferences' in the Spotlight menubar results) and you get the following:
Changing the order of the search results is as simple as clicking on one option and dragging it to a different location on the list. Clicking the checkbox next to an item tells Spotlight not to display results of that type, or to display them if the box was unchecked (as you can see I don't show Contacts in my results since I don't know anyone).
The below graphic is a little before and after action of my Spotlight results for your viewing pleasure:
How do you like to order your Spotlight results? Let us know below.
The results on the right are much better for what I'm usually looking for: the name of a cool app that I need to write about or something that I wrote many days ago. That's why I've kept Applications as my first result, but bumped up Documents and PDF Documents to the second and third slots. You should note that the 'Top Hit' and 'Definition' results are always shown in Spotlight's results.