How tough is it to get accpeted top Law school like Harvard or Yale?

The top law schools are competitive. For example, Harvard only let in 16.5% of people who applied.
http://hls.harvard.edu/dept/jdadmissions/apply-to-harvard-law-school/hls-profile-and-facts/

Agree with all the above. GPA is important, and LSAT scores. Writing is also important, for you will be writing an essay with your law school admissions. Writing skills will help with success in law school.

Besides grades, there are other things you can do in college to prepare for trying to get into law school. If your college has a mock trial team, you can join that. You'll develop lawyering skills and that would look good on a law school application.

Also, you may want to consider law classes offered by your college to determine if you want to be a lawyer before committing to applying to law school. You can also look at interning at a law firm. That way you can meet lawyers and see what they do and if the legal field is a good fit. I decided I wanted to be a lawyer after taking business law at my college.

Congratulations on thinking so far ahead about law school! I always wanted to be a lawyer, so I understand your forward thinking view. Competitive law school admissions are, in many ways, as hard to predict as highly competitive college admissions (which, you will soon see, are somewhat random).

First, work hard to succeed in college. Law school admissions are heavily focused on an applicant's undergraduate GPA and LSAT scores - not to say that extracurriculars are irrelevant, and many law schools are considering work experience after college as almost a requirement. Unlike the MCATs for medical school, the LSATs don't test knowledge of certain subjects, so there is no particular course of study that will help you get a higher LSAT score. But use any chance you can to hone your reading comprehension and writing skills. A law school curriculum will test and develop your reading and writing skills, even if you ultimately want to practice as a transactional, tax or patent lawyer. If I could point to one trait most important to success in law school (and I submit, in general) it would be the ability to write well. Good luck to you!