If you're already in the CS program then you've got a great head start. Even 20 years ago they had a way to be admitted out of high school, and for the folks who were eligible (I wasn't) and took advantage of that it was great for them.
I can give some tips I wish I had known when I started. No guarantees any of this stuff still applies since it's 20 year old info, but I suspect some of it may still be good ...
- Aim to spend 2 hours studying or doing coursework in the library / lab for every hour you're in the class. So if a class is 5 credits it will take you 15 hours a week, 3 in lecture, 2 in section, and 10 studying or in office hours.
- For upper level math or CS courses, these are often only 3 credits because there's no section, but you still need to spend at least 15 hours a week on them (so 4 hours of work for every hour of lecture)
- Put the study hours in your calendar and stick to them even if you don't feel like you need them. If that means you get work done before it's due, that's great, now you can take it to office hours with your TA or prof and get a free check on your work before you need to submit it to be graded.
- Buy a paper notebook for each course at the start of the quarter. Attend all of the lectures and sections and write everything down the instructor presents in writing and also anything they say that might be important. It doesn't matter that the prof posts slides, notes, recordings or whatever on the website, write the material down anyway by hand because it forces you to pay attention and it helps you internalize the information. Use the notebook as your first stop when you have questions doing your coursework or reviewing for tests.
- I've heard registering for courses is still tough. You get a freebie your first quarter as an incoming student, but 2-3 weeks before the second quarter start looking at the course guide and plan what you want to register for. Approach it like you're a coach preparing for the NFL draft. You need to put down the courses you must have, and the ones you'd like to have, and your contingencies if things don't go to plan. Also pay attention to the instructors, ask around for students who have taken the courses you're planning to to get feedback on who teaches well and grades well and who doesn't -- if the course you need isn't being taught by the instructor you want, you may want to try to take it a different quarter if you can.
- Make an appointment with an advisor to get advice on your course schedule. Since you're in the CS dept, you can make an appointment with their counselors.
- On course registration day, wake up early and do your best to get the courses you want with the best schedule you can. If you can't get a course you can try showing up on the first day anyway and get on the wait list or email your advisor and ask for help.
- Do NOT try to take too much in one quarter. Try to do no more than 2 hard and 1 medium or 2 hard and 2 easy courses. Nobody will stop you if you take 5 hard 3 credit math or CS classes (assuming you have the prereqs) because it's only 15 credits, but by my thinking that's 75 hours a week of work. It's unsustainable and sounds insane but you will almost surely meet or hear about people who try it. Don't be one of them.
- If you tested out of your foreign language reqs, great. Don't try to do more than you have to, unless you're really serious about the language and want to double major in it or something. I tested out of Spanish and I should have left it that, but I stupidly spent a year taking Japanese which I didn't need and just took up a lot of mental bandwidth. If you want to pick up another language, go to language school over a summer or something, don't spend your university time on it.
- Make friends. Leave your dorm room door open as much as you can if you live in the dorms. Hang out in the CS lab as much as you can.
- Hit the gym for an hour a day. UW has a great gym with tons of fun stuff and classes. You must exercise to perform your best in school. Seriously, put it on your calendar and stick to it.
- Pick a couple CS courses a year that you're going to go hard on. Set aside extra time for them, maybe double, do your very best work, and go above and beyond on assignments. Profs will remember their best student in a course and this can open doors for you.