Being an apologist today – well, since the Internet, anyway – is a bit like being a philosopher in Ancient Greece: formal training is available through universities (“the Academy”), but it is not strictly necessary. A good apologist may be more-or-less self-taught.
I tend to think of contemporary apologetics as theology on the front lines: non-academic, directed toward the common man. The best avenues are distinctly Catholic publishers like Ignatius Press, websites like Catholic Answers, as well as blogs and even YouTube. Some of the best apologetics is very “grassroots.”
If I were to advise a young person who desired to become an apologist, however, I would highly recommend first doing undergraduate studies in philosophy (preferably at a strong Catholic university or liberal arts college), and then, if possible, some graduate work in theology (again, from a strong Catholic school). Some Catholic schools offer graduate degrees in apologetics. This doesn’t mean becoming an academic, but it does mean being forced to have a lot of pivotal skills that many self-taught apologists plainly lack.
You would be AMAZED at just how many arguments against Catholicism and Christianity in general, spewed forth from the mouth’s of atheists and agnostics, are simply invalid. The serious study of philosophy, first and foremost, teaches one to recognize these extremely common errors in every day argumentation. And once you correctly point out that an argument is invalid, you don’t even have to answer its conclusion. If one’s argument is invalid, one isn’t even saying anything substantial, that is, worthy of serious response – they’re just voicing opinions or emotions. Unless your opponent recants or tries to mend his/her argument, he or she has lost the debate, Q.E.D.