Writing a documenation, any advice?

[Electric flower]

I need to write a documentation for school project and i was wondering what should be put in it?

Thing i designed and built is an acustic switch.

[Zillolo]

Maybe this can help you:

http://en.wikipedia.org/wiki/IMRAD

[geo_leeman]

I highly recommend writing in LaTeX. 

http://www.maths.tcd.ie/~dwilkins/LaTeXPrimer/

[abaxas]

First question should always be...

Who is the target audience?

[tszaboo]

You can start it by writing an about half/one page (A/4 or equivalent) so called Abstract, explaining what you actually did, why you did it, and what problems you encountered. Then copy it here, after that maybe we can help. It will go into the documentation.