I have been a first responder. In general I agree with the comments I've read so far, especially " Know your limitations. You won't remember to do everything, you have to be careful - you have to err on the side of caution, stay within your training, and do no harm. Help will be there as quick as they can."
Do what you are trained to do. Be supportive but do no harm as some people will try to make a lawsuit out of it. Also be careful about exposure to someone else's blood. It's a very high risk problem these days.
Some scenes are not stable, as in violent crime. The police have had to clear scenes before we were able to go in and help. One of my partners looked into a window and down the barrel of a 45. One patient, "slightly out of control" missed my forearm and literally bit off 3 inches of stretcher matress.
Be careful of your personal physical risk. I flagged a fireman to chase down a bystander puffing on a pipe as we had gasoline all over the place.
Keep in mind that training is training. Training does not make up for lack of experience. I have seen green medics absolutely flake out after a bad situation, especially when someone didn't make it.
Every situation always presents its unique set of problems and the training program doesn't plant a plan in your head for everything that happens. Training teaches you the basics and the ability to think and build confidence that you can handle a situation...hopefully, correctly to the best of your ability.
And I want to personally thank everyone who has ever tried to help in an emergency. Bless you! I remember a number of times when people hindered our efforts to do our job.