For the FO's going to ATP, here is a write up for you. You'll get picked up by an ATP instructor in the morning on day 1. You give them your logbooks, written test, and certs/docs/ID. The first thing you do is a ground brief covering the topics the examiner might bring up on the oral: V speeds, landing gear, props, engine failure memory items (directional control, pitch attitude, airspeed, mixtures/props/throttles forward, flaps up, gear up, ID, verify, feather, mixture ICO), how to cross feed fuel, Vmc, and fuel. The systems questions are VERY elementary.
The Vmc discussion might be more of a problem if you're not an MEI or if you haven't reviewed that stuff in a while. Just know the four factors that cause directional control issues when single engine (P-Factor, Accelerated slipstream, Spiraling slipstream, Torque) and the factors affecting Vmc certification (Standard day, Most adverse weight and CG, Critical engine windmilling, Flaps and gear for takeoff, Up to 5 degrees bank int operating engine, and Max power on operating engine). That's it for the oral.
The flying portion could be more problematic for some. Two FO's in my class had no light twin time while myself and another FO were MEI's on the Seminole. The other guys seemed to have a problem adapting to the training environment. The checkride consists of: engine failure on takeoff, engine failure after takeoff at 500', steep turns, approach to stall clean and in landing configuration, unusual attitude recoveries, engine failure and shut down in flight, holding, VOR approach, GPS approach, single engine ILS to a single engine landing. My advice is to study the aforementioned approaches for runway 32 at KCRG. Keep yourself ahead of the airplane and always be thinking what you can do next. The examiner was nothing but fair with me, although others have said he will flip out on you if you're doing something he doesn't like.
You get a 1.5 sim session (a Frasca 142 fashioned like a Seminole), and two 1.5 flights to prepare. When these events happen is totally dependent upon aircraft availability, CFI availability, and of course weather. Good luck to all of you!