There was a lot of standing around involved as you had to be there to cover the possibility of someone needing help. When you stand around in a high visibility vest you get a lot of people assuming you know everything about the event so we often learnt the layout of the venue so that we could direct people to where they wanted to go!!!
You have to be willing to deal with whatever arrives. So everything from a sticking plaster to someone who needs an emergency ambulance and their panicking relatives. You are never on duty alone though so you do have support. You also have to be good at hiding your feelings and trying to look like you are very calm and know exactly what you are doing. That bit I was quite good at as I have spent a lifetime being able to hide my real thoughts and saying what I have learnt I should say. But can you imagine someone appearing with a bone sticking out of their leg and saying "****(&*^, that looks horrible". No, you had to show a reaction more along the lines of "oh we do this all the time, you're in good hands". I learnt a few stock phrases as I find it difficult to know how to reassure people. How I gain reassurance does not always seem to be the way some other people gain reassurance. But I was able to learn a few of the 'right' things to say to get me through that bit.I think it's great that you are interested and considering doing a one day course. Even if you remember just one thing from it then it will be worth doing. Actually one of the best things that anyone can do in first aid is just to be with the person whilst more help arrives so they know they are not alone. Reassure that help is on it's way and that you won't leave them until help arrives. That kind of thing. But of course being able to put someone in the recovery position and having a bit of experience of CPR is also good.
Whilst there is theory to learn I've found that the first aid courses tend to focus on the practical as that is important. So if you learn well by doing things then it's a great course for you.