Refer them to solid, pre-Vatican 2 literature. And this only if they express interest or come to you spoiling for a fight. If they're trying to convert you, excellent! It means they know their "faith" and the Bible. Be careful on the Bible issue. Conservative Protestants can quote circles around most Catholics, even of the traditional variety. And the Bible issue does not mainly focus on the fact that we have different Bibles, although true. Example, what most Catholics believe about Martin Luther's addition of "alone" hasn't been found in Protestant bibles since the early 1900s, not even in the King James version used by fundamentalists. It's also very helpful to know the Protestant definition of certain words we hold in common. When a Catholic says, "saved," he speaks of a soul in Heaven. To a Protestant, this means you've come to a point in your life when you made a decision to follow Christ. Usually, although not always, it's the result of a crisis of some sort and is based heavily or entirely on emotion, not dogma. To "convert" has two meanings to Catholics. To Protestants, it means to leave one religion for another. Even the words "church" and "catholic" mean completely different things. On the whole, Protestants are gnostics.
Evangelizing a Protestant also entails great humility. Trying to ramrod through, "Outside the Church, there is no salvation!" though true, will not be understood by a Protestant and is resorting to those Protestant techniques that are ineffective, mocked, and rejected. Be ready to say, "I'm not sure how to answer your question, but I'll find out and get back to you." Also, pray for the wisdom to know when it's time to back off or back out.
If asked about pervert priests, a communist pope, Catholics they know who live in open sin yet hear Mass every week, certain "Catholic" politicians, it's just as easy these days to name equally corrupt Protestants and people of all religions. Remember the televangelists of the 70's, 80's and 90's? Steer the discussion back to the Faith, not others who fail to practice what they preach. These have exactly zero influence upon what is Truth and what is error. Hopefully, you can point to the good fruits of the Faith in your own life. Just because Cardinals were found to be perverts, doesn't make you or the majority of Catholics or priests the same!
If they love a fiery argument, give them one of Bishop Williamson's sermons or conferences, one that isn't mainly about the SSPX, as that will be unknown to most Protestants. There's one he gave to what I think was called The London Forum. If that doesn't start a serious dialogue, nothing will. But be careful who you give it to.
Also, form a friendly relationship with the person. With most people, it's the only way they'll take what you say seriously. Of course, there ARE exceptions. If you must be extreme to defend Our Lord, then do it. Don't be a Vat. 2 wussy who speaks "luv" to someone who curses or desecrates Our Lady, the Church, the Saints, or anything Holy. I once had to yell at a Baptist work colleague who mocked praying the Rosary. "Do not ever say that again!" and I walked out, abruptly slamming her door.
She came to me several hours later to apologize. She hadn't intended to offend me. Which gave the opportunity to explain that the real problem wasn't that I was offended so much as that Our Lord was offended. After all, how would you feel if I made a mockery of your mother? She gave me the usual misinterpreted verses to refute praying to Mary. I gave her a refutation by St. Francis de Sales. She read it and still disagrees, but it put an end to all mocking commentary at work. She declined to keep the copy I gave her, but she knows where I have it, in case she'd like a second look. We've remained casual friends.