The manner of preparing one's notes for preaching (if notes are used at all) is about as varied and personal as preachers are themselves. Within a range of options, preachers ought to feel free to adopt any method that helps them to be as comfortable (or uncomfortable) as necessary.
Generally, it would be wise for the preacher to make use of as little notes as possible without losing coherence and impact. The preacher can choose to bring a full manuscript into the pulpit, a set of partial notes, or no notes at all. Fewer notes is probably better as long as the quality of content remains uncompromised.
A full manuscript offers the preacher the greatest amount of confidence. If the Holy Spirit can guide the preacher in the pulpit he can certainly do it in the study during the week before. If the preacher has every word laid out, there is less to be nervous about. The preacher can concentrate instead on the message and not on the way that it is worded. Of course the downside is that it can be difficult to present a manuscripted sermon while retaining the vitality and presence that would normally be welcomed in a sermon. Full manuscript preachers will want to work hard to make sure that they are well prepared so that the sermons are not merely read but confidently and artfully offered to people in the moment. A sermon should not feel like it came out of a can but that it is something that lives and breathes and speaks life to people.
There are many ways to prepare a set of notes. Ideally, the manuscript sermon will be laid out, not in typical paragraph fashion,
...but in a manner that is more readily viewed at a glance.
A larger type font could be helpful.
As can be bold print.
Ask to see the notes of preachers you respect to see what people are doing and then find something that makes sense for your personal style.
Many preachers have found it helpful to prepare a full manuscript in order to discipline their thinking but to leave the manuscript aside when it comes to preach. The challenge there is that the preacher not feel crippled by the need to replicate in the pulpit, the finely crafted language that exists in the manuscript. The preacher needs to be able to communicate freely.
Another approach is to prepare some kind of partial manuscript. This again takes many forms - everything from a few ideas and key statements on a three by five card (or a post-it note in the Bible), to several pages of typewritten script. Sometimes preachers will record the detailed arguments but leave the stories and illustrations for extemporaneous delivery. Some preachers prefer to craft their statements in unfinished phrases...
...forces a more oral style...
...discourages pure reading of the text...
...offers an extemporaneous feel... ...without locking the preacher in...
The amount of notes prepared by the preacher will be dictated by things like the Pastor's experience level and their natural skill in speaking extemporaneously. Generally, less is more, as long as quality is not sacrificed.
Extemporaneous preaching has a long and rich preaching. Often misapplied by those looking for short cuts in preparation, preaching without notes usually requires an extra effort in the assimilation of a sermon, over and above the normal work of sermon discovery and construction. Preaching without notes is not usually practiced by novice preachers, but by those who are seasoned enough to feel comfortable speaking to people without the security of notes. It is "working without a net." As with the high-wire artist, the payoff can be spectacular. But then again, so can be the fall. Preaching without notes allows for the greatest possibility of connection with the listeners, but it also bears the most potential for incoherence. It is not simply "winging it." This kind of preaching is extra hard work.
It should be noted that preaching without notes is not the recitation of a memorized manuscript. The preacher does not need to be on the platform trying to recall those things that have been formerly committed to memory. This can be crippling. The preacher, rather, is working out of the overflow, sharing from a heart and mind that has well assimilated the truth and stories of the sermon.
Preaching is communication
Whichever means a preacher choses, it is well to remember that preaching is not about the preparation of a set of notes, but the communication of a message that comes from God and offers benefit to those who will hear. Whichever means will help the preacher achieve that end most helpfully is the method the preacher ought to chose.