As someone enjoys religious discussions with their friends (and pretty much the only Christian amongst them, never mind Catholic) my advice is keep it polite, respectful and engaging. Be as willing to listen as you are to put your own point across and focus majorly on what you have in common, rather than why you are different - there are many, many traits of commonality, not least of all because the faith is, essentially, in the same thing - one God. We also share ideas of charity, many of the prophets (just not in reference to divinity) - from Abraham to Jesus, and a great deal of common history - from Solomon to the Moors in Spain.
Then the discussion over what you differ on becomes more friendly, and more interesting, and their challenges to you will help you explore and understand your own faith even better as well as enable you to understand their perspective more. And you have to understand where someone is coming from to be able to have a good dialogue with them.