It depends on the type of speech you're giving. If you are presenting to a group of children, you'll deliver information differently than with a group of professors. This is the demographic, the type of person you are addressing.
The three persuasive techniques include:
pathos- Using emotional appeals. For example, if you're giving a speech about the environment, you want to tell people about the dying animals and earth and tug at their heartstrings to convince them to change.
logos- Logos is used when discussing logical appeals. If you're delivering the same environmental speech, you could use logos by telling people it benefits them, their food, their children, their wallets, etc. by switching to green energy. This forces them to see the logic in what you're arguing for.
ethos- This is an ethical appeal, which is more complicated. Basically, ethos can be used when you reference something very credible. For example, if Jane Goodall were to be giving a speech about the environment, she would be using herself as an ethical appeal, because she is very trustworthy on the subject. You, delivering the same speech, won't have the same credentials because you aren't a scholar in that field. However, you can use ethos by quoting Goodall, or using her research, showing a credible source.
If you're demographic (audience) is a bunch of farmers, concerned about their money and farms, you should use logos to show them they can save money. If you are talking to a group of young students, maybe use pathos to make them feel the emotions behind your issue, as that is something they will remember. If you're talking to professors, use ethos and apply a credible source they recognize, so they feel you know what you're talking about.
Hope this helps!