Web service Discovery mechanism enables client to locate 
and discover web service on the net. Web service discovery 
mechanism  provides a discovery document , this discovery 
document is written in WSDL and provides all the 
information about web service, e.g.
1. its location
2. What methode is provides.
etc..
Following are the steps to consume a web service:-

1.Add web reference to project.
Enter url of the web service to locate the web service and 
its methods.

2.Add reference to namespace of web service on the page (eg 
using MyWebService)

3. Create an instance of web service class (e.g. 
MywebServiceClass obj1= new MywebServiceClass();

4. call the required method (eg. int x= obj1.GetAge();)