Keeping a record of what you're doing while delivering emergency medicine is extremely important. Prehospital records not only communicate up the medical chain, but they become a part of the patient's official medical record and may be used in court at some point down the road.
I like to think of my notes as a way to organize my thoughts for radio transmissions and if the record is structured well, it can even prompt me to ask the right questions (like SAMPLE and OPQRST guides).
I've never found the perfect notebook or "run sheet." I've found water proof ones. I like those for obvious reasons, but they're not always organized around medical. I always carry a blank flip notebook somewhere on my body or nearby - just in case I need some space to write down critical information. It's come in handy for all sorts of things.
From a medical perspective, I like formal run sheets. Nothing too fancy. Just enough for me to write down response times, demographics, chief complaint, results from my interview and assessment, treatment given and people involved in care. Run sheets are not easily available though, and they tend to change from jurisdiction to jurisdiction.
In a CERT or a basic first responder environment, I like simple. The Professional Vital Statistics notebook from Portage provides 72 pages of double sided-single page mini run sheets. Each page can be torn out and handed to a medic when they arrive.
These books come in packages of three for under $10. They fit neatly into a basic EMS jump bag and, while they don't contain everything I like to see in a run sheet, they do a nice job with the basics. I'd feel comfortable handing this to my relief as part of a patient turn over.
The books include space to record contact info, time, date, chief complaint, vital signs, a brief history, treatment and some general notes (maybe used as overflow). One page per patient.
I don't expect to go through three books unless I'm deployed to some major disaster, but I like to keep one in my car, one in my bag and one as a floater - maybe get's tossed in my wife's car if I'm headed out somewhere. For under $10, you can't go wrong.