Most people I know that investigate UFOs would give their left arm to be the first to arrive on the scene of a UFO crash, however if one is going to respond to an incident of this magnitude, you just can't go rushing in without preparation. There is a long list of people who didn't give UFOs the respect they deserve, and they paid for it with their lives.
While safety is primary, we also want to make sure that we do not contaminate the scene, or handle any evidence improperly. Following some basic rules can preserve the integrity of the sight, and perhaps keep you from making a fatal mistake.
The first thing one should do when arriving at the crash site, before even walking away from your vehicle, is glove up. Some people think that means just putting on a pair of gloves...not true. To properly "glove up", one first puts on one pair of gloves, then pull your sleeves down over the gloves. Next put on a second pair of gloves, but this time fit the glove over the end of your sleeve, then tape around the glove to form a seal with your sleeve. Now you are properly "gloved up".
The next step is to put on a respirator. You will want to make sure that you are using one with new filters, and that the filters are properly rated to keep out anything that could be potentially harmful. It might seem a little bit extreme, especially if you are somewhere in a warmer climate, but choking to death on an unknown pathogen is probably not very comfortable either. I also prefer a hood as well, since anything airborne might not be too good for the skin either. My personal rule of thumb is: Don't leave anything exposed!
Next item to have out is your geiger counter. Only approach a crash if you have some way of reading the radiation levels! Even then, exercise extreme caution, and anytime you get an unsafe radiation reading, immediately back out and call your State Director, or Chuck Modlin. Do not risk any further contact until you have gear on site that can protect you from any potential radiation.
You are going to want to walk the site then, to survey the area that is involved, and then you will want to use your tape to mark off the area, and to keep people out. Only one (1) person should go into the area at a time. You do not want a lot of people going into and out of the area, possibly contaminating the area, or even tracking evidence out with them. The less people in the area, the better. Make sure to list in your control notes who the person is that is going in the area, and what they do there.
Once the area is marked off, you will want to do a complete radiation survey, then you will want to use your metal detector and do a thorough sweep for any debris that might be evidence. Whenever you get a hit with your detector, you will want to place a flag so you can come back once your grid is set up to excavate the material. Remember to photograph everything, making sure to shoot from the different cardinal directions. Any shots of evidence should be taken from directly overhead, looking straight down, and make sure you have a scale in place for reference.
Being able to think on your feet is vitally important in situations like this. One can't possibly know what they might encounter at the crash site of an alien object. Since we don't know the conditions of their world, what they breathe, eat, drink etc., we don't know how anything even as simple as the atmosphere inside their craft could potentially affect us. Taking precautionary steps beforehand can not only improve your chances of survival, it can also help to ensure that you have a solid case after collecting your evidence.
If you don't rush, you think out the situation beforehand, and remember to follow these simple guidelines, you will greatly improve your chances at a crash site. Remember if at any point you run into something that could be potentially hazardous and you're not sure how to proceed, call your State Director for advice.
I hope this helps reinforce protocols for crash site investigation. Remember to share with all of your friends, and come back for more!