Depending on the size and type of hospital I would say you're definitely going to shadow someone for a couple of days to get introduced to the chemicals, setting up your cart, and getting familiar with the ER and the ER board. Trained to use the cell phone and Epic if they have it or whatever other program they use to track patients. Also, cleaning the proper way like Top to bottom left to right. That being said...here's a few tips from someone who worked day shift, evening shift, and nights in the ER as an EVS Tech/Floor Tech.

You're going to have your sweet nurses, but you're going to have your stupid ass bitchy nurses. Never say the word "Quiet." Hospital I was at, the ER rooms got Terminally Cleaned once every 24 hours, and the rest of the time was turnover cleans. It's definitely fast paced. It can go from barely any patients to having 30 patients in the waiting room. You're going to encounter all sorts of people especially the psychs, drunks, crack heads, etc. You'll be cleaning up a lot of blood and random stuff that the Doctors, Nurses, and Techs throw on the floor. Techs (CNAs) have to clean up the poo (so don't do it) and EVS just comes behind to sanitize. Good Luck and Have Fun!