I've heard good things about this one and had a friend use this one and pass as well. Personally, the best advice I can give is work practice problems, work practice problems, work practice problems and WORK PRACTICE PROBLEMS. Working practice problems helps you not only get familiar and comfortable with the material and types of questions being asked on the exam, it trains you to answer the questions quickly. Remember, you have between 5-6 minutes (on average) per questions (closer to 5 minutes if you want to allow time to check). Some questions will only take you 2 seconds. Others may take a full 10 minutes or so. The key is being ready for all of it. For this, I HIGHLY recommend the complete Complex/Imaginary test set. I also recommend finding time to work the NCEES practice exam completely through like a simulated "real test" after preparation. Give yourself time to work this, grade it and come back to places where you stumbled.
Second thing: you're going to need reference material. For me, I took School of PE and used the notes and practice problems as my primary "go-to." If something wasn't in there, I had the Camara Power Reference Manual. For NEC stuff, the School of PE notes had a great set of summary pages on where to find major articles as well as some of the major themes and concepts the PE Exam likes to ask on the NEC. Having a NEC book tabbed with the article numbers (buy the ones they sell) is critical to being able to finding material quickly.
Third thing: What I call "supplemental" materials. I had the Chapman machines book and needed it for a couple of problems. I also had the Blackburn relaying book. It has a great section on symmetrical components and per unit analysis. Since not everyone uses per unit everyday, I'd really focus on that. Any question the PE exam gives on symmetrical components will more than likely (but not always) be conceptual or ask about a certain sequence network. The Blackburn book has all of them already drawn out.
For econ, I spent minimal time studying here. Any question they give you will be a "plug and chug" type question where you dump numbers into a pre-canned formula and spit out the answer. Be able to recognize the wording of questions in order to know which formula to use.
Other than that, PRACTICE and KEEP PRACTICING. You can do it!