Peter Mead over at Biblical Preaching has a series going on Preaching without notes that I referred to in this post. In his first post he described why preaching without notes is a valuable method.

In the second post which can be found here, Mead emphasizes the HOW. Mead's method can be summed up in one word, "internalization."

What You will say not How You will say it

He emphasizes first that it is not about memorizing the whole talk. This is a recurring theme among those who preach without notes and also public speakers. This is a key that is worth repeating, in most cases you do not have to memorize every word. It is important to memorize "WHAT" you will say, and not "HOW" you will say it.

Mead states:

It is probably worth memorizing the big idea, perhaps the statements of each move or point if you are going to state them explicitly, the opening few lines and the concluding few lines. Beyond that, it’s all about internalization.

The Manuscript in Internalization

More could have been said by Mead on internalization. Also more should have been said about having a manuscript that flows sensibly. In other words, it is easier to memorize a sermon that flows in a way that makes sense, than one that doesn't. However, following Mead's methodology will do this because he states that one should type out the whole manuscript. This is Mead's main method, it seems, to internalize the message, he states:

This manuscript allows you to work carefully on specific word choices and phrasing. The work of giving close attention to the manuscript is surprisingly effective at internalizing the wording so that it comes out again when you practice the message and/or deliver it.

Another important component is hinted at in the final paragraph, namely having a strong spiritual and prayer life. He states:

Preaching without notes is not about special memory skills. It is about full preparation that leads to the preacher being very at home in the preaching text. It is about prayerful preparation that allows the message to soak into the very fiber of the preacher’s life.

As always, go ahead and try it. Even if you don't do it every time, preaching without notes can cause your messages to soar. You are much more dependent on your preparation and the Spirit than you are with a manuscript. You are also much more fallible and can make bigger mistakes. However, with practice one can find one's best way of putting together a sermon that can be preached without notes.