Have you ever wanted to totally weird your friends (and everyone within a 20 mile radius) out? Here is how.

[edit] Steps

Straight away, you need to stop caring about what other people think. Stop caring about your image. Allow yourself to be seen humming in public, or skipping around carefree in the street. Your reputation does not matter- you are an oddball now.
Cultivate your image, make everyone think you are weird. It won't work if you just start being weird and random after being a serious person for years. If you already have a reputation for being normal, just slowly ease into being weird, you will be able to say you changed as you got older.
Invent words, places, and customs. Invent a holiday, and give it a weird name, then force all your friends to celebrate it.
Invent an Imaginary friend, and then make everyone believe you actually think they are real. Save a spot for them at lunch, do homework with them instead of another real friend, and just involve them in your life.
Wildly fluctuate the tone and ppitch of your voice.
Have a catch phrase. Make it something nobody else has used before, and nothing too cheesy.
Get a nickname. It doesn't have to describe you at all, in fact, it's better if it doesn't.
State the obvious. Or maybe the things that should be obvious, but aren't to everyone around you.
Personify things. Talk to a bush, become best friends with a desk, or go out with a fire extinguisher.
Once you have a successful weird image, word will spread of your eccentricity and you could be a perfectly normal person but still be seen as as weird. At this point you have achieved your goal.

[edit] Tips

Don't take offense if someone calls you weird. Take it as a compliment.
Don't go overboard. Take it easy at first, then gradually build up to being an oddball.
Say simple stuff like "I'm such a freak, you?" or "Hey my plasma friends."
Say random jokes, ones that might not even be funny.

Don't be too creepy, people will just think you aren't all there in the head.
Don't do all of this stuff in front of a teacher or other member of authority, they may refer you to a therapist
Remember, some jokes can be hurtfull, so be carefull not to offend anybody too much. There is a limit to what you can say about somebody.