Where to start....
I have been precepting for 25 years or so. I find that to start, I just have the new associate work with me to watch what I do. Then we talk about the critical thinking that ED nurses do in all aspects of our care...from where we put IVs to the why's. I stresss the recognition of "sick" vs "non sick" appearance and always plan for the worst case scenario and how to rule out things using assessments and history taking.
I go over the A-B-C method of assess and intervention of all patients.
When ready and the new asociate has learned "my routine"-- I start by giving her 1 patient-- usually a level 3 or 4 ESI acuity. They focus on assessing and learning how to document their findings. I take care of the tasks of IVs, etc until they are proficient at the nursing assessment
stuff, and then we add the IVs, etc.
ENA has orientation modules as well that cover soup to nuts of systems assessment.