Well, I don't feel like I'm the most qualified person to discuss this topic, but I do have a few thoughts to share... would *love* to hear others' thoughts, though!
Discipleship is such a broad term, and it happens in so many different ways. Basically, it's the process of helping others become more like Christ. And that can happen through big groups, small groups, gentle encouragements, loving rebukes, etc... I've been discipled in all those ways and I've tried to disciple others in all those ways.
For me,
love has been key in discipleship. Like Jory always says, people don't care how much you know until they know how much you care. I Corinthians 13:2 says that if I "can fathom all mysteries and all knowledge... but have not love, I am nothing." And I think that truth applies particularly to discipleship. I've been most deeply impacted not by people who had really good things to teach me, but those who had good things to say AND showed me that they loved and cared about me. And when I've discipled others, I've found that it's not all my "words of wisdom" that have made the biggest difference, but the simple fact that (by God's grace) I've loved and tried to show people that I care.
And when people know that you care, they'll follow your words, yes - but they'll also follow YOU. Like Jessica pointed out, SO MUCH of discipleship is in leading by example. People follow your walk, not your talk. Your character WILL be imitated. Whatever you do, you give others permission to do (learned that one on mission trips!

. I have a dear young friend that I've been discipling for a year now, and her mom thanked me for holding her daughter accountable to be loving toward her sister, because the mom had seen a lot of improvement in that area. However, the bigger thing to her mom was that this girl had seen how a person with her personality (we're very similar, both quiet and reserved) could live a godly, loving life, and had set an example she could follow. I have also noticed this in my relationship with my AIM mentor - I don't say this to build myself up (to God be the glory) but just to illustrate the point that the way you LIVE matters so much more than what you SAY. As disciplers, we should live so those following us can apply Hebrews 13:7: "Remember your leaders, who spoke the word of God to you. Consider the outcome of their way of life and imitate their faith."
Again, I know there are many others on this board with so much wisdom to share on this subject, and I am eager to learn from all of you! These are just a few things that I've learned about discipleship over the years.