Whether you're making a sales pitch, or just asking your parents to let you out until the afternoon, it's important that you sound and look convincing. The most important thing you can do is really mean what you mean. Using confident body language and speaking or writing clearly will also show that you are credible and serious.
Steps
Method 1 of 3: Use Body Language

Step 1. Make gestures and expressions
Moving your hands and making facial expressions while speaking can make you sound confident and convincing. For example, when you say something positive, smile a little and open your eyes a little more. If you don't move at all while talking, people may get suspicious. On the other hand, it is important not to overdo it. For instance:
- You can laugh a bit if you say something funny, but don't hit the table and act like it's the funniest thing you've ever heard.
- Likewise, if you're trying to convince your parents to increase your allowance, don't start crying. Instead, calmly present the real reasons why you think you need more money.

Step 2. Avoid gestures that are distracting
Certain gestures and actions can indicate that you are nervous. While talking to someone, you should be aware of your actions and make sure you don't do things like:
- shake you off
- rock you
- set the pace
- tap
- lick your lips
- play with your hair

Step 3. Practice good posture
Standing while you speak radiates confidence and makes you appear more convincing. However, don't be rigid. Just keep your head up, your back straight, and your feet slightly apart.

Step 4. Don't lean on things
Leaning against a table or something else while talking suggests nervousness. On the other hand, standing firmly indicates credibility. If you are talking to someone and you don't know what to do with your hands, try leaning lightly on your hips. This pose may appear safe and will prevent you from leaning on something else.

Step 5. Make eye contact
Looking someone in the eye while speaking is one of the easiest ways to appear convincing. However, don't open your eyes too wide. You should also break eye contact from time to time. Remember that you are trying to join someone, not win a staring contest.
- Even when addressing large audiences, making eye contact is important. Find a few audience members you can see clearly and take turns looking into their eyes. Look up periodically to catch a glimpse of the rest of the audience.
- Remember that in certain cultures, it is considered rude or inappropriate to look someone in the eye when speaking.
Method 2 of 3: Speak Convincingly

Step 1. Emphasize important points
When you get to something really meaningful, speak a little louder or slower. It doesn't mean you should yell at someone or make yourself difficult to understand. However, speaking a little more emphatically on the points will make you appear convincing.
For example, if you tell a potential customer that your product is the best on the market, calm down and emphasize while saying something like "Our product outperforms ALL of our competitors by 25%."

Step 2. Choose a speech that sounds natural
In general, you should try to speak normally, even when trying to sound convincing. A natural tone and normal wording will do the job themselves.
- Using big words and hackneyed phrases won't make you sound credible. Stick to language that is easy for listeners to follow.
- Speak at a volume that is close to those around you rather than sounding high-pitched or mumbling.

Step 3. Take a deep breath to regain your composure
If you feel like you're getting nervous, start talking too fast, or do something else that makes you seem unconvincing, calm down for a moment. Take a deep breath and then continue.

Step 4. Give others space to talk
A good speaker will stop when appropriate and let others take their turn. Sharing rather than dominating a conversation shows that you have the confidence to listen to others and still hold onto your own thoughts. Doing so will ultimately make what you say more believable.
The above is important even when talking to your parents. Give them a chance to speak, listen to them, and try to convince them of your point of view

Step 5. Avoid evasive or deferential language
The way you express what you say matters as much or more than the actual content of it. If you're trying to sound convincing, it means avoiding saying things like:
- "Well, hmm …"
- "I think maybe I …"
- "This could be the case …"
- "I really do not know."
- "If it was [X], then it could [Y]."

Step 6. Use vivid language instead of abstract
Being as specific as you can while speaking shows that you mean what you mean. Try to include as many details, stories, facts, etc. as you can when talking to others. For instance:
- If you're doing a sales presentation, don't just say something like "Our product has improved efficiency for a lot of people." Instead, say something more detailed, such as "99% of our customers report that our product has improved its efficiency ten times or more."
- If you're trying to convince your parents to let you out late, don't just say something like, "You never let me do what I want!" Try saying something more specific, like "You said if I improved my grades we could talk about letting me have more privileges."
Method 3 of 3: Be Compelling When Writing

Step 1. Avoid idioms
Exaggerated language can appear even when you speak, but it has a tendency to appear in writing even more frequently. Don't be afraid to write simply. Remember that your goal is to appear clear and convincing. If the audience doesn't understand your writing, it may seem like you're hiding something or you don't really have anything to say.
- Don't use lofty language when it's inappropriate. For example, if you can say "improve" instead of "mitigate", consider doing it.
- If you use technical terms like "synergy", make sure they are known and used by the audience.
- Likewise, if you use slang or informal language, make sure the audience understands what you mean.

Step 2. Clean up your writing
Writing something sloppy, full of errors and typos, or not formatted correctly will make it look the opposite of convincing. Show your readers that you are credible and mean what you say by polishing your writing.
- Always check before sending something.
- Support what you say with specific evidence whenever possible.
- Cite any source of information you use.

Step 3. Allow yourself to be you
Showing your personality and appearing natural in writing is more challenging than doing it while speaking. It is because readers will not have the ability to see you and read your body language. Try to do your best so that your writing shows who you are and what you are trying to convey.
- For example, if you're writing a college admissions essay, don't just say you want to be a doctor because you think that sounds good to admissions committees. Instead, draw a picture of what your interests and goals really are, no matter what you think someone else wants to read.
- Have someone you trust read your writing and tell you if it "sounds like you."