For the writtens, just to get them out of the way, think Gleim and Sheppard and stuff like any other checkride.
For the teaching -- and this is where I goofed in my prep for my first ride, think Kerschner. Read Kerschner. Practice teaching. Teach teach teach.
My DPE explained this in this very simple way:
You need to be able to teach how to fly, how all the systems work, and how to navigate, and plan, all the regulations and where to find them and why they exist, and good decision making -- to someone who walks in and doesn't even know their car has an oil cap.
From numerous discussions with folks, this is the number one reason folks don't pass the first time out -- it's about teaching, not about passing a checkride.
Oh, but you'll also have to fly to commercial standards while demonstrating and talking to the person in the other seat about this lesson's objectives and also making sure to be instilling in them that they will be pilot-in-command, not you. They need your guidance to learn how to do things and how to think ahead to the next thing, while letting them do as much of it as they can without overloading them beyond frustration and setting them up for "wins" not failures. They'll fail all on their own, that's why you're there, and they need to feel safe while exploring their newfound skillset.
The two worst things you can do are taking over the aircraft too soon (kills their confidence and makes them wonder what they did wrong) and taking over too late. Additionally you need to lesson plan such that they can eat the elephant one bite at a time and explain it in simple direct language.
The other huge trap to fall into is thinking the examiner is a high time pilot with lots of knowledge that you're trying to impress, like a typical checkride -- primacy will burn your butt here. They're simulating someone who literally just walked into the building from the street that you've never met and you need to take that person and show them how to be PIC, step by step. Much more slowly than you'd spit out information to someone evaluating you and your knowledge.
For this engineer, used to teaching advanced tech classes to people with a heavy background in the jargon and terms used in my industry, and coaching similar people -- it's a b**** trying to back up and remember what it was like to learn simple stuff one building block at a time in my youth.
And that's where I went wrong. Re-ride is Wednesday and I've been studying and practicing a completely different way since the initial ride at the end of October.
Think baby steps. If the examiner wants to simulate that they're further along, they will tell you and you can assume certain knowledge, but not before.
Prep to teach.