This is an old trick, and people often figure this out if you’re not very careful with it.
Rather than aiming for direct complements while asking for favors like “Hey, that’s an amazing jacket. Could you help me move some furniture around this evening?”, try something like “Hey, I know you’re usually flexible, but would you have time to help me move around some furniture this evening?”
Even if you’re not naturally confident, it’s hard to fake it and difficult to distinguish. In essence, confidence communicates to the other person that you’re already convinced that you’re going to get whatever is in question, and subtly nudges the opposite person to let you have it.
However, like with everything, balance is key. Overconfidence may come off as arrogance and turn the other person off.
This can be a little tricky, but it works like a charm. Let’s say you need to paint your room and would like your friends to help you out.
Now, they may be reluctant. But you could subtly slide in something that could motivate them to join you. For example, tell them that since you’d be tired after painting the whole day, you plan on chilling later with some booze and pizza. If they like booze and pizza, they’ll likely tag along. If they don’t like booze and pizza, then you should look for new friends anyway.
It’s far easier to persuade people with logic, than with anything else. If you’re able to show the other person why it is that you’re right about something by sharing your thought process, they might just agree with you.