Whether you feel it or not, if you appear confident, you are more likely to persuade the other person that your point of view is right. You will appear more authoritative, which people respond to positively. Remember, fake it until you make it!
Know what you're talking about
People will not be persuaded unless you can prepare to answer the "why" question. Do all your research around the topic, and make sure you know the facts!
Prepare for arguments against you
If it's a tough topic, the other person may well have a good reason why they don't think the way you do about that subject. Make sure you think about what their objections to the decision may be, and prepare counter-arguments that make your point difficult to say "no" to!
No one likes giving in to an angry or emotional person, especially in a workplace environment. Even if you think it's not going your way, make sure to take a few deep breaths, and to talk slowly. This will help your point come across stronger.
Read your audience
Who are you talking to? If you are talking to your boss, informal language isn't going to cut it. Are you talking to your family? Then formal language is going to sound very odd! Monitor your language to fully connect with the person you are talking to.
Gauge their reaction
Look at how the person is reaction to what you're saying. If they look angry, think about toning down your language, and go softer on the subject. If they look like they're agreeing, you have some room to press home the point!
Picking your time
No one likes to be approached about a pay rise when they are about to go into a big meeting. Make sure you pick a good time for the other person, as they are the one you want to help you! Ask if it's a good time to talk, and if not, ask to arrange a time that works for them. Being flexible will help you seem more approachable, so when the time comes, they are more willing to talk to you!
What are your top ways of persuading people? Let us know @office_fruit