One thing I’m suprised no one has mentioned yet is to review every QRH procedure. Every possible light, annunciator, caution message, warning message, non-message failures like cracked windshields etc. it’s a great way to familiarize yourself with exactly what procedures exist in the QRH, and also to have a general working knowledge of what is going on so when it actually happens you have an idea. It can also help to piece together systems knowledge. I would say it’s definitely important to have a basic understanding of your aircraft’s systems before diving into the QRH so you can really apply your systems knowledge and build more complex information in your mind.
It was ironic I had actually just been reviewing non-EICAS message QRH procedures for my aircraft not to look long before *BANG* had a windshield crack on me. Since it was fresh I was already familiar with the procedure so it was better for me to understand system consequences (windshield heat / integrity, speed limitations, pressurization, altitude limitations etc.) and form a game plan while working through all the issues.
Also in a previous plane I flew there was a nefarious caution message that if uncorrected (isolating the faulty bleed system) in 30 seconds would lead to a warning message and loss of all pressurization requiring an emergency descent. Unless you knew where that QRH procedure was and had it down cold there was no way you’d get to the corrective action before it began depressurizing the airplane. With certain MELs I was aware of this and would have the QRH procedure tabbed and ready to go as well as briefed in case it did happen.
For non QRH planes I think it would be prudent to review all abnormal and emergency procedure checklists. Then beyond that find scenarios that are not covered by those checklists and dig into systems and think through the problem. Likely a good idea to then come with questions ready for when training begins if you aren’t so lucky to get an in person systems class.
There is certainly way more to studying systems, but on a more applicable level these are techniques to study that I have found very helpful.