In addition to the built-in OpenERP modules and the various settings that can change the way OpenERP functions, there is also a growing collection of custom OpenERP modules written by the community. When you find a business requirement for which you believe you may need to do some custom module development, take the time to go to the OpenERP application repository and search for modules that could perhaps fit the purpose. Even if the module is not exactly what you are looking for, there can often be a lot of valuable code in those modules that can help you with your own module development.
You can find the OpenERP application and module repository at apps.openerp.com.