Equity Research Interview / Modeling, Writing Test Preparation

So I'm gonna be applying to various Boutiques in August / September (some are later). I've done the networking (I have quite a few referrals on the table) and I have work experience (EY M&A - 1 year). I'm Graduating my undergrad in December of this year (Non-Target). 

My question for you is: I know that some banks require a writing and modeling test. For those of you who went through the process before (and were successful), how did you prepare for the various tests etc.? How did you prepare for the interview? What sources did you use? 

I'm pretty good at excel and I'm currently brushing up on my three-statement modeling skills and DCF / Multiples valuation. 

Any advice? What am I missing? 

thanks in advance.