A general question

Hello I posted before but i think it was a bit of a stupid question. Im really not having much luck with this web services and SOAP thing and wondered if anyone could help me out. I might ask some pretty dumb things but thats because im not completely clued up about everything and im still trying to work it all out! When i try to build something, most of the tutorials i find seem to use services from the xmethods site, is this mandatory? How would i write something without them, can i just have my client, server and my own WSDL file? Does anyone know where i can start off writing something that is 100% mine instead of referring to xmethods?? Any help is very much appreciated, its hard starting out learning something new! Many thanks Laura