In persuasive writing, the introduction is critical as this is the point in which you define your position. You absolutely cannot be wishy-washy - pick a definite position. This becomes your thesis statement. There are many techniques that you can use when structuring your introduction. Good writing "hook" readers in some way, encouraging them to keep reading. I have included a link to a great resource that I use with my own students when teaching persuasive writing.
The introduction is not the place to state your reasons. Instead, you can open with a story, a statistic, or a quote. Ask the persuasive question (Should music lyrics be rated as movies are?), then answer it with your thesis which strongly states your position.
Well it depends on if your for or against. Tell weather your for or against it. If your for some points might be that it keeps people from being sidetracked from overly showy clothes and that it keeps people safe and publicly acceptable. If your against it I would go with that it withholds freedom of expression and it makes it harder to be yourself and feel confident which in turn could have aneffect on grades