It maybe a little bit too early to ask this question. If your target is the graduate school of UC Berkeley, I recommend you should do the following:
1. maintain very high GPA throughout your four year study. As far as I know from my friends who studied there, students in Berkeley grad school particularly in computer science (or EECS) usually have GPA of 3.7 or above in their undergraduate study. He is surprised to learn that more than half of the grad. students in the department have GPA higher than 3.8 in their undergraduate study!! Unless you come from big name schools that are famous for tough and difficult coursework, the higher the GPA the better.
2. For GRE, I don't think you need to prepare until the end of year 2. However, you may need to take GRE subject test in computer science.
3. Your English capability is very important. Since you will be asked to write personal statement or essay for the application, your writing skill need to be very good. The personal statement or essay usually include your study goal and plan. Why do you do want to study graduate degree of your subject?
4. Build good relationship with professors in your department. You will need three recommendation letters for graduation school.
For your first two years, build a solid foundation is very important. Maybe some relevant working experience will be helpful.
Sorry that I cannot type Chinese from my computer, hope that you understand what I write.
my friends and my experience