I took the civil exam, not mechanical, but in the final week leading up to my exam I stopped working problems and focused on organization. Organizing my notes, references, materials, etc.. I made sure I had a way to transport my materials to and from the exam and devised a method to access them quickly and easily during the test. I set up binders with materials and clearly labeled everything. I put together an exam day "survival kit" with snacks, cough drops, asprin, cold meds, etc (I was suffering from a cold the week leading up to the exam). The only problems I studied at all was a few engineering economics type questions, "simple" subjects that I thought would be good to review, but I ceased all my real studying.
+1. The survival kit is one of the least discussed, but equally important things for the exam. My kit included klenex, some granola bars, hard candy, some drinks, a seat cushon, a wristwatch (I don't normally wear one), some ear plugs (in case the silent shuffling of papers got annoying), a sweatshirt, my reading glasses (I only need them when working on the comp, but just in case), a backup calculator, and about $10 in loose bills & change (vending machines, parking, etc).
I recommend visiting the exam site the day or two before to scope out parking, access, etc. When I did it, I found out that the other half of the building was hosting a home & garden convention and that there would only be 1 reserved parking area for exam takers. Because of the convention, ALL parking had a $5 fee and since I don't normally carry cash I would have been screwed.
Preparing your lunch the day before and bringing it with you would also be recommended. You don't really want to count on being able to just run down the road and hitup a drive thru.
Get to the exam early. The exam starts at 8, but they want you settled into your seats by 7:45 to start going over the rules, which means you really need to be there between 7 and 7:15. I showed up at 7:30 and was scrambling to get ready in time.
Don't change your normal routine. Eat your usual dinner & breakfast, go to bed at your usual time. Try to avoid caffene (coffee, energy drinks, etc) if you don't normally drink them, and if you do, limit yourself to your usual amounts.
You have spent hours and hours preparing yourself for the material on the exam, the last week should be focusing on preparing yourself for the physical ACT of taking the exam. Be ready to sit in one place for two 4-hour stretches with only a 30-45 minute break (they give you 1 hour, but you need to be back in your seat at least 15 minutes before the session begins). Be ready to adjust clothing as the day goes by because the room temp never stays constant, the adrenaline changes how your temp adjusts and how you feel. Be ready to write for 8 hours. I know this sounds simple, but since so many of us use computers for our day-to-day activities, you forget how cramped your hands can get if you have to constantly write for that long.
Biggest help for me: Take the day off before the exam. I mean COMPLETELY off. No work, no studying, no thinking. Go out and do something you find enjoyable and relax. I actually went out and test drove new cars. Nothing is more fun than absolutely raging a car that isn't mine, then just handing the keys back to the salesman, thanking him for his time, and leaving to the next dealership.