My advice for the final two weeks is, number one, take a timed practice exam if you haven't yet. After that, I would work on maybe one to two hours a day of going back through practice problems that you have previously solved, just work through them again with the basic governing theories and equations in mind, like JR and IlPadrino said. Try to start thinking "big picture" - like what are they really testing me on here. It all boils down to a few basic principles that they are trying to make sure you understand, such as ideal gas law, energy balance, etc. (speaking as an enviro now). If you can think that way, you can save a lot of time on the exam by knowing exactly where to go for the equations.
The second thing I would do is read as much as possible. Some may disagree, but I say the best way to treat these final two weeks is to eat, drink and breathe engineering. Read the actual chapters of the textbooks surrounding the problems you have worked, but in more of a relaxed, not-working-problems mode. Again, start trying to "see" those overriding principles. Every day.
Final day before exam: spend about 3-4 hours going through the NCEES practice exam again. You've done it before, so it won't take more than that amount of time. Don't do anything else, except maybe some more reading. I thought that was an excellent way to "visualize" the day prior to the exam.
