Not with wisdom and eloquence.

1 Corinthians 1:17 NIV For Christ did not send me to baptize, but to preach the gospel---not with wisdom and eloquence, lest the cross of Christ be emptied of its power.
This verse is surprising. How much time do we preachers spend on delivery? This verse implies that the more time we spend on “smooth and clever”, the less power in the message, the message being the gospel. I suspect that Paul’s delivery was heartfelt, direct, personal and dignified, but not clever or smooth. His letters are strong, comprehensive, detailed and personal. A full reading takes time. I have no idea how long Paul would preach publicly for, though in his teaching amongst believers, he would go on into the late night, as I gather from the young man who fell asleep and fell out of the window in Acts 20:9.
 Most western church services have a time set for a sermon. This is a time of teaching, rather than preaching, yet it is appropriate, in my opinion, that the proclamation of the gospel takes place during this time, as this is an opportunity to call people into faith. Yes, our teaching ought to be clear, and a smooth delivery seems to be an expectation for both speaker and listener, but a great performance is not a mark of the Spirit. Hollywood has invaded the church. The west is so well entertained that we do not accept rough edges even in a sermon. Good sermon preparation is about seeking Gods will and submitting to his word in our own lives, as we meditate in the depths of a passage of scripture. Out of that, we will have something to share, something to confess, and a re-referencing of our thoughts and plans in the light of a God who sent his Son to bring us into the light of his great salvation. Power is a good word. It sometimes is translated to “dynamite”. But the power of the gospel is not an uncontrolled explosion. Moreover, it is the strength and wisdom to grapple with and domesticate the stubborn, unrepentant will and heart of any and every human being. The raging storm that caused the disciples to lose hope while Jesus slept in the boat, was calmed by a single strong word from our Lord. It is his word, not ours, that enters and subdues the rebel will. But he can and does use people like us.