This is how I instantiate my graphic.
var pt = new esri.geometry.Point(jsonobj.longitude, jsonobj.latitude, this.map.spatialReference);
var sms = new esri.symbol.SimpleMarkerSymbol();
var infoTemplate = new esri.InfoTemplate("<b>THIS IS INFO</b>");
var graphic = new esri.Graphic(pt, sms, infoTemplate);
this.map.graphics.add(graphic);