I had set an aggressive schedule to complete course work in EWM and appear for certification. My main source of prep was SAP EWM material with ERPPrep questions as an additional source. It would not be an understatement to state that ERPPrep was critical for me getting certified.
The ERPPrep format allows you to practice in the exam format (i.e., answer 80 questions in 180 minutes) or a mini-format which lets you take 40 questions. Personally I liked the mini-format as it allowed me to practice in chunks as against spending 3 hours.
I would highly recommend including ERPPrep in your preparation as it will significantly improve your shot at getting certified. Wishing you all good luck.
Prep for EWM Certification