Interruptions in your workflow can really make getting things done an incredible challenge. To keep those interruptions and distractions from ruining your focus, here's a quick tip from GTD guru David Allen: file the interruptions as notes in your inbox.
The simple technique moves those interruptions to the side so you don't have to dwell on them for longer than necessary. A key step, though, is to make sure you go back to your inbox by the end of the day to deal with the interruptions.
This method puts you back in control over your day, much like planning for interruptions (also with scraps of paper) can.