Always keep a crowbar (a knife is great if you have access) or other decent sized, solid object quickly accessible by where you'd sleep. I'd say keep a gun or something more potent, but something tells me that's not the best suggestion for a kid - so a crowbar would do best. If you can't quite get that, a hammer or even a pointy flathead screwdriver can at least give a thief a nasty surprise.

If you're serious about security, proper training or at least searching ways to disable intruders is a good start, as the aforementioned crowbar would be utterly useless if you couldn't do a proper swing with it.

Have your phone and grab video/picture evidence as much as you can, though your safety in the event intruders act hostile towards you is the key point.

Typically, common house thieves wouldn't push you to go actually put into good use what I mentioned above. I just happen to be in a community where the average intruder is usually high on pot or crack and as such must be put down one way or another if they end up in my house. Your best bet is a relatively obvious camera system pointing at all the key points of whatever property you're on... but that's not really for you to do unless you can convince your parents to do it.

How necessary I would say this all is entirely depends on the nature of your neighborhood.

fireman777throw a lamp at the thief? why does everyone say him or he? could be a girl too.

Simpler to say "he" and from my personal experience, out of a few dozen shady people I've caught on my property, I've only seen one girl, who was the main fellow's girlfriend.