You have made the right decision, and are undertaking a very important
step in your life!
1. If you are a high school student, find out if your school offers Latin and/or Greek. Take as much of this as you can before you graduate. In any case, begin planning now to go to a school with a good undergraduate Classics program. You can see a list of universities with Classics programs in the US here.
2. If you are a university student and you haven't taken any Greek or Latin, all is not lost! Quickly, find out what Classics courses your school offers, and start taking them now! If the semester has just begun, you may find that there's still time to drop and add courses. Do this if possible. If not, take Classics as soon as possible. If you are already a junior or senior, you'll have to do some scrambling, but there's still time. I once had a classmate who was an MA student in English, had not studied Classics, but wanted in. He worked hard and now he's doing a PhD in Classics at a good school. You can see a list of universities with Classics programs in the US here.
3. If you are a university graduate or a full-fledged "grown-up", it's harder to convert. Check to see if your local university or community college offers any Latin or Greek through a Continuing Education Department. At worst, you can always go to the public library and check out some works from Classics in translation. It's a poor substitute for the technicolor of the original, but it's the best way to acquaint yourself with the amazing world of the ancients in a short time and relatively easily.
4. If you've converted to Classics, let me know about it. Perhaps I can direct you to someone who lives near you and who can help you in your exciting new journey. Also let me know if you're a former something-else (eg, Journalism major, Underwater Basket-Weaving Studies major, etc.) who is now a Classics believer and who has an inspring conversion story. The world needs to know! E-mail me if you have any questions.