(Bernardo Strozzi, ‘The Sermon of St. John the Baptist’, ca. 1644 )
Apologetics has to be done in love, with humility, soaked in prayer.
It's mostly amusing, but sometimes annoying to be in a field of work that most people have never heard of. “You say you're sorry all the time?!”
It's good to laugh at yourself. But seriously, my “job title” originally came from Plato: the ancient Greek philosopher, and his book called The Apology: which was about Socrates, another philosopher, vigorously defending himself against false charges of corruption at a trial in Athens (he wound up being sentenced to death).
That was the initial meaning of apologia: which is also a biblical word (more on that below). Through common usage it became, simply, “saying you're sorry.” But even today, an effective apology (especially to one’s spouse!) often requires a good explanation: which goes back to the root meaning.
The Christian (or, more specifically, Catholic) apologist is one who defends Christianity and demonstrates that Christianity is reasonable and credible. In practice, it usually means removing objections or “roadblocks” that trouble or confuse people. We apologists are on the “front lines” between the Church and the opposing secular culture.
But apologetics is not merely “reactionary” in nature. It's a positive endeavor, to bolster the faith of Christians, and make them more confident that faith is compatible with reason and solid thinking. We are to love God with our mind, as well as all our heart, soul, and strength, as Jesus said (Lk 10:27). If we know why we believe what we believe, then we can more ably and enthusiastically share our faith with others, as God and the Church call us to do.
The most famous Christian apologist is C. S. Lewis (1898-1963), of Chronicles of Narnia and Shadowlands (film biography) fame. He was an Anglican professor of English literature, who also wrote apologetics books. Like many of the most influential apologists, he was not formally trained in theology. This was also true of G. K. Chesterton (1874-1936): the most beloved and respected Catholic apologist: who was a journalist by trade, and never attained any college degree at all.
Since apologetics is ideally mostly on a “popular” level, I think it's good that many involved in it are not theologians writing to other scholars (as academics do). The idea is to educate the masses. It's more like being a mixture between a preacher and a high school teacher (or maybe a private tutor), than like a college professor.
Many apologists are converts from Protestantism. This is good insofar as we converts understand Protestantism from the inside, and can, therefore, more effectively argue against it where we believe it is in error, and also point out the significant common ground with our “separated brethren.”
I'm very grateful for the many good and true things that I learned as an evangelical Protestant (from 1977-1990). I utilize them every day: especially the love for Sacred Scripture, and the concern for evangelism that evangelicals are known for. Converts don't believe that becoming a Catholic is going from “bad” to “good”; but rather, from “very good Christianity” to the “fullness of Christianity.”
Some of the more well-known Catholic apologists today are Scott Hahn, Karl Keating, Patrick Madrid, Jimmy Akin, and Steve Ray. It's a thriving field, with lots of great books, websites, radio shows, and conferences. One might say we are in an age of “apologetics revival.”
But unfortunately, many people view apologetics as by nature an arrogant, unsavory, “triumphalistic” activity: putting down others and quarreling endlessly with other Christians and non-Christians. It's not that at all (rightly understood). Yes, we contend for what we think is most true, but we can still respect what is true and good in other positions: held in good faith.
We defend positions that we honestly hold and wholeheartedly believe to be true. But at the same time we can ecumenically and happily acknowledge the many areas of common ground with other Christians and even other religions, while not compromising our own Catholic beliefs at all. These goals are entirely harmonious.
The classic apologetics Bible passage emphasizes the spirit in which we are to engage in it:
1 Peter 3:15 (RSV) but in your hearts reverence Christ as Lord. Always be prepared to make a defense [apologia] to any one who calls you to account for the hope that is in you, yet do it with gentleness and reverence;
It has to be done in love, with humility, soaked in prayer. The apologist must always keep in mind that it's God Who causes anyone to become convinced of the Catholic faith, or to become a committed disciple of Christ. It's all by God's grace and His power. The apologist is merely a vessel. That gets our eyes off of ourselves. Any gift or ability that we have comes from God. As we used to say in the evangelical community, “evangelism is one beggar sharing what he has with another beggar.”
Another related verse is Jude 3: “. . . contend for the faith which was once for all delivered to the saints.” My favorite of all (what I've always sought to live by, as a model) is St. Paul's self-description:
1 Corinthians 9:19, 22-23 For though I am free from all men, I have made myself a slave to all, that I might win the more. . . .  To the weak I became weak, that I might win the weak. I have become all things to all men, that I might by all means save some.  I do it all for the sake of the gospel, that I may share in its blessings.
God saves anyone who is saved, but He chooses to involve us in the process. Thus, Paul states that he could “save some.” Since he often urges us to imitate him, that is our mandate to evangelize and “do apologetics.” Obviously, folks have varying levels of ability to do so, and very few specialize in it, by vocation, but we are all called to share our faith in some fashion.