Check the Date: Looking for a file that was created during a specific time period? Spotlight has a handle on dates. Typing date:today will bring up files you created, read, received, or opened today, including applications, if you have that category in your search results. You can also use the date:keyword with yesterday and tomorrow (for the latter, Spotlight can't tell which files you're going to use or create, but restricts its results to iCal events and to-do items).
You can also specify more parameters, such as whether a file was created or modified on a certain date, an exact date, or a range of dates. For example, you can type created:12/25/13 to find files authored on that date; this is a good way to find photos you took on a specific date. Type modified:<11/30/14 to look for files changed before that date; or type created:1/1/12-12/31/14 to locate files created between these two dates.
Search by Kind: One of the most useful ways to narrow down a search is by using kind:keyword. This allows you to restrict your list of results to a certain type of file. For instance, if you type time machine kind:pdf, Spotlight will pull up only PDF files containing the words time and machine. You can also limit your search to email messages, music files, System Preferences, applications, and more.
Spotlight can look for files created by specific applications, as well as certain file formats. Searching for kind:mp3 or kind:tiff will find files in one of those formats, and searching for kind:pages or kind:powerpoint will show only documents created in one of those programs.
For a list of useful keywords, see My Kind of Keyword, below. But remember, for the keywords to work, you must have the appropriate categories enabled in Spotlight's preferences.
My Kind of Keyword