Wouldn't it be nice to know who was armed, the type of weapon they were carrying, and where on their body the weapon was concealed? Unfortunately, the first indication many officers have that someone is armed is when a weapon is used against them. While someone carrying a concealed weapon will often exhibit traits that an alert officer can recognize, this is not always the case. Therefore, you must assume that anyone may be armed until you determine otherwise.
Watch the hands
Always pay close attention to hands. While it's true that other personal body weapons such as elbows, knees, shins and feet can cause injury...hands kill! If someone's hand is concealed, you must assume that person may be armed. If you wait for confirmation that the person is armed, you will have placed yourself at an extreme tactical disadvantage.
"Take your hands out of your pockets." Do you really want him to take his hands out of his pockets? If he's clutching a weapon, you've just granted him permission to draw it. Instead, consider having a person with their hands in their pockets face away from you and slowly remove their hands, one at a time, on your command.
If a hand furtively reaches into or is pulled from a pocket or from the waist or groin area, you should be doing one of two things, depending on the distance between you and the suspect. If you are within lunging distance, move away from the threat by stepping forward at a 45 degree angle, pivot toward the suspect, and shove his near side shoulder/upper back. This will hinder his ability to draw a weapon and allow you the opportunity to draw yours. If you are further away, create distance with lateral and rearward movement (preferably toward cover) while drawing your firearm.
Visually search clothing
A firearm, edged weapon, bludgeon, or improvised weapon can easily be concealed in clothing. This is particularly true during winter, since heavy jackets often completely conceal the waist area, which is recognized as one of the most common carry locations for concealed weapons.
Be particularly leery of an individual wearing a snow jacket at noon in mid-July. Although it's not illegal to wear inappropriate clothing for the weather conditions, it certainly should be viewed as a red flag. While the individual may simply be cold for some reason, he may be wearing the jacket to conceal a sawed-off shotgun!
Look for unusual bulges in clothing where weapons could be concealed. Is the silhouette of that jacket distorted around the waist only on one side? It could be a large cellular phone...or a firearm!
Monitor body language
Often times, armed individuals will give several indications that they are carrying a weapon. Look for warning signs, such as a person with their arms crossed, hands in pockets, hand hovering around the front waist area, etc. In each case, the armed subject may be trying to keep their hand(s) close to the weapon for quick deployment. Additionally, people who are not used to carrying a concealed weapon will often touch the weapon to ensure that it's still there (especially in cases where the weapon is not carried in a holster). There may also be psychological reasons for touching the weapon, since it can represent power to the possessor.
Pat down (Terry Frisk)
Obviously you must have either consent or reasonable suspicion that a person is armed to justify a pat down of their outer garments. In either case, you should expect to find a weapon. Since most of the time, your search does not result in the discovery of weapons, it's easy to become complacent and simply "go through the motions," rather than conduct a thorough and systematic search. This is unacceptable, since missing a weapon even once could have tragic consequences.