A few more things:

Math and calculation:
• Become good at mental arithmetic - Being able to quickly estimate the value of an expression is very handy. While others are running through the calculator again, you can check your work in your head. Even if you can only get within an order of mangnitude, you'll be ahead of the rest. Read a book on "number sense" - there are lots of tips and tricks.
• Learn your units well - English or metric, be able to convert and apply dimensional analysis quickly and effortlessly. Don't leave out the silly measures, either, such as slugs and BTUs.
• Learn the common constants - Know the values for pi and e and the square root of 2 and such; know that a day is 86,400 seconds long or 1440 minutes; know that feet per second are about one and a half times miles per hour; know that one horsepower is about 750 watts; know that an acre is about 208 feet on a side; know that the earth is 40,000 kilometers in circumference. All of these come up all the time and things will go faster if you don't have to look them up to estimate a quick result.

Work the system:
• Research your profs - If you have trouble with a prof or have one that is hard to follow, check them out on the web and in the library. They'll be pretty flattered if you happen to know some theory they espouse or some research they've done. Sometimes you can see where they're coming from if you can see where they've been.
• Talk to your advisor and dean - Most of the time, they'll be flattered that you've come to them with something important (make appointments, be on time and be polite), rather than annoyed. I've seen a "concerned group of students" cause a tenured professor to be called on the carpet and forced to improve his substandard teaching habits.
• Save your homework and tests - These should be passed on to future generations of students. Sometimes dorms or student associations or clubs have files. If so, contribute as much as you take.
• Work in groups - Find some other students to work with. In courses like thermogoddamics or kinetics, where you mostly learn by doing zillions of problems, you will save countless hours by going to a room with a whiteboard and working them out together. Make sure everyone "gets it" and everyone participates and everyone actually works the problems out for themselves, of course, but use the group to figure out the approach and method for the solution. If you can keep this group together for your whole four years, you'll probably add at least a half a point to your GPA.

Above all, have fun and don't sweat the small stuff. If engineering isn't fun to you, by all means change majors. And, don't worry, after your first job, no one will ever care what your GPA was again.