I think there are a few tips buried here that might help you make disciples on Facebook (or any social media platform).
1. Don't be shy about how God is present in your life.
2. Don't be a religious drone, simply spouting or reposting what other people say. Have your own material. Talk about the personal ways God is speaking to YOU. If you are on social media then invest the prayer and time to do it for the glory of God.
3. Avoid the crazy issues that get everyone inflamed UNLESS you commit to A. learn about the issue from various viewpoints and B. pray a ton about it and get direction from God about what to say.
4. If someone writes you a note to say whats up, drop a little spiritual bait maybe, a note about how God has blessed you or offer to pray if it applies (then actually pray for them).
5. Once people reach out to you, you gotta respond. Don't get nervous about it, their eternity doesn't rest in your hands alone. The Bible says God is drawing them, and that the Holy Spirit teaches them. So proceed in a lighthearted yet intentional way.
6. Don't bombard people with all your favorite books, songs, a free copy of the Bible, and more. I used to do that, it didn't work. Someone else's faith is going to be different from yours, which God will reveal to them in their own time. Not saying don't send ideas now and again, just don't deluge.
7. Let people respond, and a bunch never will after that first interaction. But some definitely will, and its glorious not only for them but for you.
Consider that your Facebook page (along with everything else in your life) is useful to God for drawing people to himself. Are you tuned in to allow him to do it? Go for it.