How do you convince our parents?

1) Don't ask them when they are in a bad mood, ask them when they are in a good mood and having a good day, because if they're in a bad mood then they are more likely to say no.
2) Give them reasonable reasons to whatever your trying to convince them to let you do.

3) Explain that it would mean alot to you and give them lots of compliments like "i love you" or "your the best parent in the world", but say it like you mean it so they fall for it
(unless it's true).

sorry if these don't work, i know how it fells to have to convince my parents all the time to let me do things.