what should i know before using a webservice

Question

I made a program call a webservice GeoIpService using wsimport for knowing ip location. but it look like local class method call program written in java.because wsimport give classes for use. i call in main method

            String ipAddress = "17.21.55.143";
    GeoIPService geoIPService = new GeoIPService();
    GeoIPServiceSoap geoIPServiceSoap = geoIPService.getGeoIPServiceSoap();

    GeoIP geoIP = geoIPServiceSoap.getGeoIP(ipAddress);
    System.out.println(geoIP.getCountryName());

for using this web service i have to know so many thing like,

1- which generated class will give the ip location information.

2- i have to go through a pre defined process for getting ip address create a instance of GeoIPService , create instance of GeoIPServiceSoap by calling getGeoIPServiceSoap() method and so many..................

i am new to learn webservice,so i have so many doubt about this

• what should exactly know before using a webservice.do i have to know what kind of information provided by a webservice if yes how.
• using wsimport i have generated classes. how i know which class going to give me information and what is the procedure to get the right information without exception.how user does know and user may be a java client or dotnet client or c++ client.
• is each language client generate language specific library using same WSDL with own tools.for example in java wsimport.
• may i am asking many silly question. but i really confuse regarding webservice what information must we have before using a webservices written in any language from a java client.

Thank's.