The problem with children is, there's no User's Guide, no owner's manual, no 800-number you can call for Tech Support. And so as a parent you just have to wing it when a child asks if she can, for example, play with the WeedEater.
Or maybe she simply wants to dye her hair green and get a few eyelid piercings and a forehead tattoo before she goes to the Slayer concert with a guy she met through MySpace.com who promises to drive very safely on his motorcycle.
You're the parent: Make the judgment call. You're no dummy. You simply refuse to be manipulated by a spoiled brat of a child. And thus you must make the hard decision to say no, absolutely no, incontrovertibly no, unless of course you think that by saying no you will disappoint her.
In my house I'm the steel pillar of supreme authority, and the kids know I cannot be budged, swayed, guilt-tripped or bribed. Their only hope is to exploit my inattention to the finer details of things, and so we have conversations like this:
"Dad, can I borrow the car?"
"Sure. [Pause. Thinking hard.] Wait, are you old enough?"
"Daaad, I'm already 12."
"Yeah, but what's the legal age for driving?"
"I don't know. But I'm only going to Massachusetts."
"Oh. Okay. Cool. Put gas in it."
I'm not the kind of father who constantly passes the buck and says, "Ask your mother," because that's weak. Besides which, the kids know that their mom is definitely going to say no, and I can win points with them by sometimes saying yes. The distance from the obvious no to the surprise yes is proportional to my popularity with the children.
"Who's your favorite parent?" I often ask them, teasingly. "Who always lets you have a fourth helping of ice cream even when you are on the verge of lapsing into a diabetic coma? Who's the one who lets you stay up until 4 a.m. watching slasher movies while playing computer games on Mom's laptop until you somehow destroy the hard drive? Huh? Who?"