No need to prepare specifically for the ATP-CTP course beyond what is necessary for the written test, where all the conventional advice applies.
You might want to check out the Turbine Pilot's Flight Manual to gain a better understanding of systems such as pressurization, high altitude aerodynamics, etc. There's also some info in the PHAK and AFH on turbine systems/operations.
For a CRJ newhire course, you should have a solid understanding of instrument procedures and it will help if you can read Jepp charts. Read a little about its systems, autopilot, etc. It is better to know a little of everything than detailed knowledge of a few things. Have a decent instrument scan, particularly with a glass panel. Flight Sim can help if you don't have glass experience.