How to call webservice in asp.net using jquery?

<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script>
   <script type="text/javascript">
     $(document).ready(function () {
       $("#SayHello").click(function (e) {
         e.preventDefault();
         $.ajax({
           type: 'GET',
           data: '{"name": "' + $("input#name").val() + '"}',
           url: 'http://localhost:2312/Webservices%20Practice/Service.asmx?op=Hello',
           contentType: 'application/json; charset=utf-8',
           dataType: 'json',
           success:
             function (data, textStatus, XMLHttpRequest) {
               alert(data.d);
             },
           error:
             function (XMLHttpRequest, textStatus, errorThrown) {
               alert(textStatus);
             }
         });
       });
     });
   </script>