gmaps.js

You can geocoding this way:

GMaps.geocode({
  address: $('#address').val(),
  callback: function(results, status) {
    if (status == 'OK') {
      var latlng = results[0].geometry.location;
      map.setCenter(latlng.lat(), latlng.lng());
      map.addMarker({
        lat: latlng.lat(),
        lng: latlng.lng()
      });
    }
  }
});

You can define either address or lat and lng. Also, you must define callback, which will use results of geocoding and status.