Help needed with commas before dependent clauses

[SusanSmith]

I can never figure out when a dependent clause needs a comma before it. Where would you put commas in these sentences and WHY? They're not actual sentences that I'm planning on using. I'm just giving examples of the kind of sentences that give me trouble, so I'm not looking for advice to rewrite the sentence to completely avoid the issue. I'd like to actually understand how to punctuate properly.

Violence and crime rule on the streets of L.A. where gangsters wield knives and guns.

Saturday Night Live is surreal in its silliness as the actors depict a mouthless man winning an audition for a toothpaste commercial.

Some people see toy tea sets as an attempt to keep women in their "proper place" in life by indoctrinating girls through the use of stereotypically female toys.

I'd like you to pay me next week if that's possible.

He says he can come with us if my parents will be there.