Are you thinking that facts will always win an argument?
Facts and data have limited power to persuade. Present us with facts and we'll start filtering. We'll quickly accept facts that support our view of the world and forget or reject facts that don't. We'll even be working on counter-arguments while you are talking.
Intelligent people wouldn't do that? Intelligent people are more likely to come up with creative counter-arguments.
Find common ground. Present your argument in ways that show we are aiming for the same goal.
The classic case is persuading parents to immunise their kids. 'Immunisation is safe' and 'Immunisation doesn't make kids autistic' won't work as well as, 'Here's a way to ensure our kids are safe from the big diseases'.
Want to persuade your executive team to spend money on a more expensive machine than the Kamakuza model they think will keep their costs down? Focus on 'return on investment' - things like efficiency, reliability (so keeping production uninterrupted) and lower maintenance costs.
Let's say you are in a meeting. You want to persuade your colleagues to see the benefits of adopting a shared digital calendar.
Your presentation seems to be going well until Fred leans back on his chair and announces, 'It's not worth the hassle. My diary works well for me. I'm not changing.'