As illustrated above;
Single file formation-maintain a 2 second interval between you and the bike in front of you. This formation is utilized on curvy roads and when hazards are encountered.
Stagger formation-maintain a 2 second interval between you and the bike your following in your half of the lane. The other half of the lane will put bikes 1 second ahead of you and 1 second behind you.
Trikes-Three wheeled bikes ride the center of the lane. The first bike behind the Trike will assume "leader position" (inside half of the lane).
Stay out of the blind spot!
In close quarter riding if you cannot see the face of the rider in front of you, in HIS mirror, he can't see you.
Here's a link to the MSF website to review various videos on topics, such as Group Riding.
How much distance does it take you to stop? Brian S was kind enough to share this "Braking Calculator" he found. Click the link and check it out!