First thing you HAVE to do is take an LSAT prep course. Testmasters is hands down the best course. It has increased the score of everyone I know. It increased by score by 19 points!
www.testmasters180.com
Obviously doing well in undergrad helps as well, but the LSAT will make or break you for bigger schools, especially somewhere like Georgetown.
I would also recommend reading a book about law school. The best start to finish book is "Law School Confidential by Robert Miller. Really good insight from applying to school to studying to applying for jobs once school is done.
A final bit of advise is to apply EARLY! The applicatin process is really easy because it is all online now. So the only hard part is writing your personal statement. Work on it early and often as well. Though don't stress too much as grades and LSAT are what will make or break you anyhow.
Good luck!