When Spotlight plays up, I first remove a file named com.apple.spotlight.plist which is the preference file. Sometimes it gets corrupted and removing it can help resolve some issues
If that does nothing, then I reindex Spotlight by opening up the Spotlight pane of System Preferences (you'll have to find it manually 😛 ) and adding my hard drive to the Privacy tab, closing System Preferences, reopening it and removing the hard drive from the Privacy tab. This might take a while to reindex depending on your machine and the amount of files you have. 🙂