While each service (Army, MC/Navy/CG and AF) has a slightly different way of having the guidon render a salute while in formation, there is another salute rendered by a guidon that each service requires when outside of a formation when the guidon bearer is on his/her own.
The only authorized giudon bearer salute when in formation for each service ends up looking like this:
When a guidon bearer is not in a formation (either walking somewhere or standing and holding the guidon) and is approached by an officer, there is only one authorized salute, which is different from the salute pictured above. This salute is not authorized while in formation.