First, we note that this commission is given by Jesus' authority and is bolstered by his presence. His authority is total and complete. As the resurrected Messiah, he has been given the keys to the kingdom and can dictate the terms of the kingdom. But his authority is not totalitarian; rather, it is benevolent. In giving this command about expanding his kingdom, Jesus promises his presence, with the disciples "until the end of the age." What Jesus commands us to do, he also empowers us to do.
Second, we are to make disciples. We are not to make converts only. This is made clear when Jesus said to baptize and teach. We are not to baptize only, but also to teach, and to teach for obedience. This means we must grapple with the material of discipleship so that we first one, so that we can lead others into the same obedience.
Third, the content of what we are to teach is the five-fold division of material in Matthew as represented in the five teaching blocks in Matthew. The core of discipleship and life in the kingdom is found in the sermon on the mount in Matthew 5-7. This is the basic teaching about discipleship that must be one and taught to others. Chapter 10 contains teaching about preliminary mission, specifically, about how one begins to go out to share the good news, searching for people of peace, and learning how to trust God. The growth and expansion of the kingdom is mysterious, and Jesus touches on this in chapter 13 with encouragement to trust God and let him build the kingdom. As the kingdom builds, churches spring up and begin to develop. So, in chapter 18, Jesus provides instruction for how the church is be with on another (hint: he focuses on relationships, not doctrine). Finally, as disciples mature and churches grow, there will always be the struggle to focus on minutiae and on things we can't control. So, in chapters 23-25, Jesus reminds his disciples to be alert, stay awake, and be diligent in their faithful walk.
This is the path of discipleship. In Matthew, the idea is to be always growing in discipleship while also discipling others. From the sermon on the mount, we listen to Jesus and follow his example, throughout the gospel. As we grow in discipleship, we baptize others and teach them to obey. Much of the teaching about obedience will be shared in real life, as you teach by example and the disciples see your obedience in action.
The great commission is a serious call, but it is a summary call as well, to go back to the beginning, to grow as a disciple, and to lead others into discipleship.