Finding a dead body can frequently be a traumatic experience. Even when the body is not a loved one, personally encountering death can have wide range of effects on individuals.
The most important thing to do is to remain calm. Then, if you are able, confirm death without disturbing the scene or body, and contact the authorities (9-1-1). Feeling for a pulse, or breathing, will generally be okay. If the deceased has clearly been so for some time, there is no need to confirm a pulse or breathing. Additionally, you can call 9-1-1 before doing anything, and allow the operator to walk you through what to do.
Death and the Good Samaritan
Sometimes, an injured or unconscious person may just appear dead, when in reality they need medical assistance. If that's the case, then calling 9-1-1 immediately might just be what saves a life. If you have received some emergency training, such as CPR, you might consider trying to help until professional medical help can arrive. However, any help you personally offer should be coordinated with your call to 9-1-1.
Most states will absolve a Good Samaritan of personal liability if they stop to provide help to someone who is injured, dying, or in distress. Shockingly, in Vermont, a person can actually be found liable if they do not stop to render aid. Good Samaritan laws protect people who try to help from later being held liable for things like a broken rib that was the result of administering CPR. However, recklessness and/or gross negligence will likely remain unprotected. Other than Vermont, no states require a person to offer assistance to those in distress.
Suspicious Scenarios Surrounding the Deceased
If you come across a dead body in an odd place, or under suspicious, or nonsensical circumstances, do not touch anything and contact 9-1-1. Recently, a man was discovered dead in his car, which had received a small mountain of parking tickets with him dead inside. Generally, a 9-1-1 operator will instruct you on what to do, and will ask questions to determine if there is anything you can do until authorities arrive. If you can see a weapon, or other evidence that a crime was committed, you may want to consider moving to a safe location while waiting, but do not, under any circumstances, move or disturb the body.
Usually, after reporting a dead body, you will just have to wait until authorities arrive so you can provide a statement. Police and medical examiners or paramedics will arrive on the scene to confirm death, and determine whether evidence should be collected and/or preserved. While there are ways to anonymously report the body to the police, doing so could actually lead to some suspicion.