Dear brother,
I try to give my best now, shortly. This is the essence of my experiences. YOu can spare years, or decades, if listen to these:)
1: listen to other preachers, read the greatest preachers' books. It is useful to learn strong and nice expressions, parables, etc. Some good style will stick on You.
2: You must preach in a way, that your serving clothes would not be polluted by the blood of those, who You are responsible for. (Spurgeon told this)
3: In the practice, I have learnt, that I need very small thinking on the message, but a lot of prayer.
Pray for the people a lot, because, the message is given them by only the Holy Spirit!
Pray, and fast for them, so that the Spirit would break their heart, and open their eyes of heart. If You can not cry foor the people, or Your own heart's hardness, Your message will not wound any heart!
Ef 6:17-18 has a hungarian translation: take the sword of the Spirit which is the word of God, through praying prayers and supplication in the Spirit.
No other way! Most of my messages I get when praying for the people, for the church, for the hearts, even my own heart, and about the word. I pray the word, and tell even to myself first in prayer. I pray let's say 4-6x more time, than writing my sketch and reading commentaries, etc. And the same with preaching: I pray 5x more time, than I preach.
With this, You will always have fresh messages in Your heart, and will be able to preach without even any preaparation, if needed. It is like burning fire in You, waiting for being poured out.
4: You have to learn, that God is able to work in the hearts, even if You will not preach a single sentence!
Some came into the church, sat down, and hearing the word started to cry. I have not told anything on the gospel, but this young couple understood, that they need God. How? The Spirit was in work.
You must learn, that the principal of preaching is to let the Spirit of God work. If the effectiveness of my preaching is 1, the effectiveness of the worok of the Spirit meanwhile is 1 million or more:) So do not want to substitute His work with Your thoughts and style, but long for His work.
Lots of preacher do not have faith in Him. They have faith in methods, theological education, understanding, greek language, and style etc. But You, if You want to preach effectively, must have strong faith in His work.
5: If the word is weak in You, it will be still weak, when leaves You.
You must be full of the word, that You are going to preach. If YOu can not catch fire, You can not expect others to do so.
6: Preaching starts not on the pulpit, but in YOur own heart, and then in YOur family, and friends, then in the church.
You can not preach things, that YOu have no experience with. The word, that is not worthy to share with Your family and friends, before sharing on the pulpit, has no value at all. If it is not precious enough to tell it immediately to all to change their lives, it has no value to preach in the church.