how to use ng-option to set default value of select element

So assuming that object is in your scope:

<div ng-controller="MyCtrl">
  <select ng-model="prop.value" ng-options="v for v in prop.values">
  </select>
</div>

function MyCtrl($scope) {
  $scope.prop = {
    "type": "select", 
    "name": "Service",
    "value": "Service 3", 
    "values": [ "Service 1", "Service 2", "Service 3", "Service 4"] 
  };
}

Working Plunkr: http://plnkr.co/edit/wTRXZYEPrZJRizEltQ2g