Present arms is a two part command used by many militaries in the world as a sign of respect. Within the United States Military, it is executed in the following procedures:
1. If armed with a firearm, present the underside of the firearm towards the one receiving the honor.
2. If bearing a guidon, lower the guidon to a horizontal position with the lower portion of the staff resting in the pit of the right arm.
3. If armed with a sword or sabre, on the first count raise the sword vertically or at a 30-degree angle from vertical, depending on the branch of the military, with the sword grip 6 inches in front of the neck, and then on the second count lower the sword to the right side, pointing at the ground at a 45-degree angle, with the right hand or knuckle bow next to the pant seam. The true edge is always to the left during the whole procedure of "present sword."
As with all proper commands, it is to be given from the position of attention only.
Following "Present arms", the command "Order arms" (also a two part command) is given to return the firearm to the proper position of attention.
http://www.paloverde.org/rotc/afjrotc/html/manual_of_arms.HTM
