How to Become a Preacher. Becoming a preacher is a serious undertaking. You are assuming the responsibility of spiritual advisor. While the road varies for each person, the following are some basic steps that will help anyone begin on their path to preaching and sharing God's message.
While you don't have to be able to recite the entire Bible on command, you should have a very good understanding of it. Mainly because if you're going to be the leader of a church, your church members are going to be coming to you for advice and guidance. Since a lot of your advice is going to be based around Biblical scriptures, you're going to need to come up with relevant content.
Talk to your church's pastor. He's gone through all of this before and frankly, you're going to need a mentor--he's going to help you with this massive decision. He'll also let you help around his church, learning the ropes so to speak. Depending on how filled his staff it, you can eventually become an assistant pastor which performs most of the same duties as the pastor.
Figure out what kind of preacher you want to be. Determine whether your skills lie in story telling, as a great orator or perhaps you're better with one-on-one ministering. You need to know this if you want to become a preacher so you'll be effective and reach as many people as possible.
This might be hard to grasp to non-Christians, but most pastors "heard a spiritual voice"--the voice of God--urging them to work for the church. Most pastors refer to it as their calling from God.
Do missionary work. This isn't a requirement but it definitely helps when you're trying to preach the word to people and build your "flock."
Go to seminary school. This school will dive deep into teaching of the Bible and Christian theory. This will be some of the best learning you'll get on becoming a preacher. Once again, this is not a requirement, especially if you plan on being a missionary or working in small local churches. But if your goal is to be head pastor at one of the increasingly popular mega-churches, a degree is a necessity.
Practice. Preaching is like most anything else and you have to practice doing it. You may be struck by the word but if you don't know how to deliver it, it won't be any good to you or to those you're trying to reach.