How Can I Use Methods Defined in a Separate File?

I noticed that you can use “#include <file.h>” in order to obtain functions defined in the file for use. Whenever I try my own file wit defined functions in it, it does not work. I think it may be that I am not defining the methods/functions correctly. Help!

If you want to define functions that can be used by any sketch then have a look at the information on creating a library, for example: http://www.arduino.cc/en/Hacking/LibraryTutorial