This following example is a small snippet of code for a AJAX web service call to a .NET service with JQuery. We will be sending a email and name to our web service to sign up for a email subscription.

/*JS Email Subscription AJAX web service*/ 
callService();

function callService() {
  // Here we will create our data object to send. In this example we are 
  // sending a email subscription request. We will send a email address and a name.
  var data = {
          email:  $("#emailTextBox").val(),
          name:   $("#nameTextBox").val()
      };
      
  $.ajax({
    type: "POST",
    url: "/myWebServices.asmx/emailSubscription",
    data: JSON.stringify({ "data": data }),
    contentType: "application/json; charset=utf-8",
    dataType: "json",
    success: function (response) {
      if (response.d == true) {
        alert("You have been subscribed");
        //Do any work you want if the web service was successful. 
      }
      else {
        alert("Error");
        //Or throw a error
      }
    },
    error: function (error) {
      alert("error");
      //Or throw a error if service failed
    }
  });
  }