There's a friend I have who was recently baptized. He was taught about baptism, and we left him alone, and he eventually made the choice without any pushing of any sort.
He knows cursing is wrong, and he doesn't curse around me. Well, he does euphemistically. But that's a huge improvement from what he used to be like. Anyway, he continues to curse on his Facebook and he continues to like pages that are about marijuana use.
I know as a new convert it took me a while for a lot of things to sink in and truly understand how I should be acting as a child of God. So I guess my question is, would it be better to wait and see if he makes the changes on his own, or should I bring this to his attention now? What do you think?
Leaving problems alone doesn't get them fixed. But I would like to suggest that you look at this particular problem in a different way. His use of profanity and possible use of marijuana indicates that he is missing some foundational ideas and those gaps need to be filled in. Once there, the symptoms you are seeing will disappear.
Therefore, instead of approaching him with "cursing is bad," study with him about why some words are good and others are bad. See Careful What You Say as a possible approach. Or move back even further and study with him about why God said not to take His name in vain or how we honor God. See You Shall Not Take the Name of God in Vain as an example. This isn't all you talk with him about, but rather one of the topics you cover.
The same goes for marijuana. Study with him about the need for Christians to be sober because of our battle against Satan. Mention how alcohol, drugs, and even marijuana impairs a person's ability to make good judgments.
When you see a gap in someone's wall of protection, look first to see what is missing in the foundations and then build them up from there. Usually they'll fix the more noticeable problems on their own once the foundations are properly in place.
Sometimes the foundations are there, but a person hasn't made the connection yet. A gentle question of "Why are these words acceptable on Facebook but not in church?" may get a person thinking in the right direction. And if not, you may be surprised at how the person is able to justify to himself different behaviors in church and in the world, which then will lead to study about this unusual style of reasoning.
"But avoid foolish and ignorant disputes, knowing that they generate strife. And a servant of the Lord must not quarrel but be gentle to all, able to teach, patient, in humility correcting those who are in opposition, if God perhaps will grant them repentance, so that they may know the truth, and that they may come to their senses and escape the snare of the devil, having been taken captive by him to do his will" (II Timothy 2:23-26).