Informative speaking generally centers on talking about people, events, processes, places, or things. Informing an audience about one of these subjects without being persuasive is often a difficult task to complete. For example, a speech informing an audience about growing peace lilies as houseplants might ultimately persuade the audience to buy and grow peace lilies. All speech has an effect that might enable individuals to self-persuade themselves. The line walked during an informative speech, as opposed to a persuasive speech, is to not make persuasion an explicit and obvious goal. An informative speech on peace lilies might cover both the advantages and disadvantages of these houseplants; a persuasive speech would take a firm position on the virtues of peace lilies.
Analyze the audience. What can the audience be reasonably expected to know? If talking to a field of medical professional about cloning, they likely know the basics of DNA. An audience of lay people might not be so fluent in the language of biomedical engineering, and so basic concepts like this will have to be explained. Never presume that an audience has a thorough background in the subject.
Use appropriate language. What are the norms for speaking style for the audience? If they expect lots of jargon and specialized language, the speech should be peppered with such language or else the audience will feel like they are being talked down to. If the audience is unfamiliar with these technical terms, avoid using them or introduce them with an explanation of what they mean.
Explain the importance of the topic. Why should the audience listen? Will this information improve their lives in some meaningful way? Especially with a captive--involuntary--audience, a speaker must establish a connection between their topic and the interests of the audience.
Express interest in the subject material. Why should an audience listen if the speaker seems just as bored as they do? A speaker who confesses their own interest in the topic might activate the audience to share a similar interest.
Show, don't tell. Don't most people learn through doing or seeing? Being told about a process, like cloning, could be informative, but probably not have as great an impact as being shown the process with pictures or perhaps even lab equipment. Informative speeches often benefit from a demonstration or visual aid. Technology can assist "showing" when the subject is not easily brought physically into the room (imagine the troubles of an informative speech on the sun if a prop was required!)
Be specific. Informative speeches thrive on detail, and dive on generalities. If speaking about basket weaving, carefully note what types of weaving materials work and do not work for basket making. Audiences are often impressed by detail, but be careful not to become so detail-oriented that the big picture of the speech is lost (missing the forest for the trees).
From the University of Pittsburgh
Persuasive speaking is the type of speaking that most people engage in the most. This type of speech can involve everything from arguing about politics to talking about what to eat for dinner. Persuasive speaking is very connected to the audience, as the speaker must, in a sense, meet the audience halfway. Persuasion, obviously, is not entirely controlled by the speaker--persuasion occurs when an audience assents to what a speaker says. Consequently, persuasive speaking requires extra attention to audience analysis.
Traditionally, persuasion involves ethos (credibility), logos (logic), and pathos (emotion). By performing these three elements competently, a speaker can enhance their persuasive power.
Recognize that the audience is constantly processing what the speaker is saying. Nonverbal reactions are common for an audience listening to a persuasive speech--a furrowed brow, nodding head, or rolling eyes can be signals from audience members that they either like or dislike what the speaker is saying. Acknowledging these nonverbal reactions can help a speaker explain more in detail certain points.
Identify the target audience. In almost any persuasive speaking situation, there will be a subset of the audience that agrees, that disagrees, and that are undecided about the topic. Preaching to the choir--speaking to persuade those that already believe the speaker--might consolidate the audiences' beliefs but has little benefit beyond that. Trying to persuade the segment of the audience that adamantly disagrees with the perspective voiced is generally unlikely (though not unheard of). Therefore, a speaker ought to focus on the part of the audience that is undecided on the issue. Speaking more directly to this group of undecideds allows a speaker to tailor their speech more towards their concerns.
Pre-empt common objections. Many audience members might be skeptical of the viewpoint advanced by a presenter. Consequently, an orator ought to acknowledge and respond to these objections within the speech. This approach might answer some of the questions that audience members might be asking of themselves.
Most persuasive speeches concern questions of fact, value, or policy. Issues of fact are similar to informative speeches in that they review findings. The difference is that persuasive speeches make judgments about which findings are accurate. Issues of value tackle the time-honored questions of what is good, right, or beautiful. Values can be either individually, communally, or nationally held, and are thus contentious and often clashing. Issues of policy concern what actions should be taken to resolve a particular problem. Policy questions posit a problem and a solution.
Articulate the goals of the speech. Does the speaker want the audience to sign a petition, write their legislator, boycott a product, talk to their friends, buy a certain product, or take some other tangible action? Oftentimes, the conclusion enables a speaker to make a call to action that is the culmination of a persuasive speech.
From the University of Pittsburgh