[Skunkworks] Load Testing

How can one test the load that a server can support for a particular application? For example, if you have an ERP system, how can I test the performance of the server that is hosting the application? -- Thanks and Regards, Erick Njenga Nyachwaya, M: +254-725-008-790 <http://www.facebook.com/ErickNjenga> <http://www.twitter.com/ErickNjenga>