I highly recommend Magoohs book in combo with ETS books. Magosh breaks the math down better if that is your challenge. It also does a good job of teaching you how the GRE will trick you! Best of luck! https://www.amazon.com/GRE-Prep-Magoosh/dp/1939418917
Keep your GPA up, don't get lazy. You really need above a 3.0 for school's to look at you, and then at least a 3.5 or higher to get into a competitive program. Link up with your academic advisor and tell him/her/them about your goals for grad school, and ask what classes you can take that might make you look good as an applicant. They are going to be an invaluable resource and might be able to point you in a direction you might not have thought about.
Don't put all your eggs in one basket. Stanford sounds awesome, but have at least five schools to apply to. Even that might be too small depending on how you look as an applicant. I applied to 10 PhD programs and got rejected/didn't hear from 9 of them, three of which were my dream schools. The one I got accepted to was second to last, but I'm insanely happy here and don't think I would've enjoyed the school's I really wanted to go to. I got insanely lucky, but if I had only applied to one, I probably would've gotten rejected. You have time, but have a cohesive list by your Junior spring. Maybe around Junior Spring/Senior Fall, start emailing professors at these schools that you might be interested in working with. If they become your advisor, you will be conducting their research/something similar so make sure you like it and get along with them.
Study for the GRE, it's the main thing on your application that you can change relatively easily. I recommend books by Magoosh, because they really teach you how to take the test, not just quiz you on the content of it. Figure out what score you need to get into your schools, a lot of school's in my program wanted applicants in the 50th percentile. I recommend starting to study during Junior Spring/Summer and then taking the GRE at the end of Junior Summer or the beginning of Senior Fall before applications are due.
Get some research experience. I'm not sure how engineering departments operate (I'm more on the science side of STEM), but in my undergrad there were always opportunities for research. Personal anecdote: my advisor specifically picked my application out of the pile because I had my name on four separate research projects throughout undergrad, which gave me a great breadth of experience and skills in my field. Look around at your school and see what professors are working on, and then ask them if you can be a research assistant or even just shadow them for a semester. Some school's will even let you do this for class credit, as mine did.
Finally: STAY AWAY FROM GRAD CAFE. It's a forum website that a bunch of graduate applicants and their parents post on. It will freak you out, just don't put yourself under that kind of stress, everyone's path is different.
All in all, it's great that you're starting to think about it so early, but don't forget to enjoy your time in undergrad.
TLDR: for now, get good grades, talk to your advisor, explore more schools, work on a few research projects. By the end of Junior Summer: study/take the GRE, narrow down your list, email professors.
I loved these two books for practicing (especially Magoosh!! I bought them on Amazon, but look around--you may find a better price), but I'll admit I really focused on the math part since that's what I needed the most practice on. The Magoosh book really breaks down the math section into the different concepts you need to know, a lot of which I hadn't talked about in school for a long time, haha. I also recommend taking practice tests in the same setup/format as you're going to take the real test.