1. Recall those incidents when you had to persuade your parents to buy/give you something.
2. The kind of tactics/strategies you used for the persuasion.
3. How long it took your parents to give in.
1) The time when I had to persuade my parents to buy me an iPhone.
2) Whining, comparing yourself with others who have something you want and promise them to do well in studies if they get you the phone.
Emotional - Your parents love you, so they should buy the phone for you thinking that they want to get the best type of phone for you.
Threat - Threaten them if they do not want to buy the phone for you. Not recommended as it is rude and unhealthy for parent-child relationships.
Promise - Convince your parents that you are willing to put in effort to study if they put in a little more money for you.
Deal - Roughly the same as promise, having a deal with your parents, exchange of conditions.
3) 20 minutes.