You haven't specified a particular speech here so I'm assuming you're speaking generally.
Speakers may use a range of devices that are persuasive or build rapport with their audience. They will use a tone and register that is appropriate to their audience. In terms of persuasive devices, look for use of rhetorical questions, anecdotes, high modality language, use of pause and emphasis, anaphora and repetition. They might also make appeals to ethos, pathos or logos, the three parts of rhetoric (persuasion). Ethos is the authority of the speaker so when the speaker proves to the audience that he knows what he's talking about and should be trusted, this is an appeal to ethos. He might do this by providing credentials, being a well-known figure, or presenting a well structured speech that is strong in its use of persuasive language. An appeal to pathos is an appeal to the audience's emotions. A speaker wants to elicit a certain reaction from the audience so he may use devices such as the rhetorical question, an anecdote, emotive language or analogy to achieve this. The appeal to logos is an appeal to the audience's logic and reasoning. A speaker will structure their ideas so that they seem logical to the audience and they will be supported by evidence.
Ideas in a speech and the speaker's point of view will be supported with examples, quotes from others experts and statistics where it is appropriate.