First step for our groups are to minimise potential distractions. Not following these requirements is seen as very rude, and is enforced by other players more than the GM (ie, Me

)
A) Dedicate the gaming room. No TV's, Radios or Observers (unless they promise to shut it).
B) Phones on Silent. For us, a good night is a performance, and while the villain/face is giving a great speech, or the gunfire is thick and fast, nothing ruins the mood faster than a tinny '
La Cucaracha' ringtone
C) If leaving the table (for bathroom breaks, smoko's etc), expect your PC to be likewise unavailable. If in combat, wait until after your turn, and make it a quick trip unless you trust the GM to roll your defensive tests... HeeHeeHee...
D) If you expect to be interrupted during the session (expecting a call, have to leave early etc) be upfront with the group beforehand so we can expect it.
E) Have a recognised and-Gesture or Phrase that calls for attention (from GM or Player alike). We're all big kids, and the no-one should not need to be a teacher in front of the class '
Eyes this way, people. Everyone have their listening ears on? Good children...' No. Just, No.
As for dealing with distractions as they come up:
1) Use hand-gestures/key-phrases to bring focus back
2) Be reasonable. If a genuine situation occurs (family emergency, storm, etc) let it slide
3) As GM: Be interesting.
If something is happening too slowly, wrap it up.
If something is obviously boring everyone, wrap it up.
If someone is hogging the spotlight, wrap it up.
I will gladly end any situation if it's just devolved to a dice-rolling exercise. If the players have taken out 8/10 opponents, make a judgement call if the enemy have any aces to play and if not, call it quits with a '
we surrender' or '
you mop them up with no further hassles' magic wand.
Same for long-term legwork. Let the PC's buy successes to speed up gameplay (1 sucess per 4 dicepool) and move on. If the players want to squeeze anything further out of a scenario, roll those dice specifically, but keep the game moving.
eg If the face has 16 dice to play, and is up against a street snitch, just hand over the info

4) Win our younger days, we had the In-Game scenarios of '
A dragon flies overhead and looks at you hungrily', or the '
Miniturret pops-out where you stand. It's close enough for you to see the camera lens re-focus on your face'. However we don't use these anymore as it gave the In-Game-PC's a line on a complete tangent to the game at hand. Whole point was to regain focus, not start a brand new scenario....