Speeches don't have to be invented from scratch. Telling a personal story is a great way to come up with something quickly: since you already know what happened, you'll know what to say. For example:  At a wedding, you could tell a funny story about growing up with the bride or groom. At a funeral, you could tell a story about how kind or generous the deceased was, or about how they influenced you. This is another way to rely on something that's already out there, rather than having to come up with something on the spot. Think of an inspiring quotation, some lyrics to a song, or a famous saying that applies to the situation when you're speaking. Start off with that, and then discuss it a bit. For example, imagine you're giving a toast at Frank's 70th birthday. You could say something like: “They say you can't teach an old dog new tricks. Frank here's proving them wrong. Who else would have the courage to start running marathons in retirement?” Rambling on too long is the number one thing that can go wrong when giving a personal speech. It's much better to avoid saying too much. Keep your speech brief, focusing on two to five main points or examples.  For example, if you're toasting the groom at a wedding, stick to just two good stories about your friendship. If you see people in the audience do things like turn away, talk to each other, check their phones or watches, or fidget in their seats, you might be rambling on and losing their attention. If this happens just quickly cut to your main point and say “thank you” as a way to close. Even practiced speakers can get nervous when asked to give a talk on the spot. Control your nerves by taking a deep breath before you begin, and taking brief pauses every so often while you are talking. Focus on pronouncing your words clearly, and not speaking too quickly. Many people feel nervous about giving a speech, especially with little notice. But if you show the confidence to give one, they'll applaud you. Plus, they'll all be so happy not to be the ones giving the speech...

How would you rephrase that briefly using Chinese?
讲一个你熟悉的故事。 引用别人说的一句话来开始演讲。 简洁明了。 说话要清晰、从容。 自信一点。