//Create your sharelet with desired properties and set button element to false
    var object = SHARETHIS.addEntry({title:'Spread the Word'},{button:false});
    //Output your customized button
    document.write('<a id="SpreadTheWord" href="#" class="SpreadTheWord">Spread The Word</a>');
    //Tie customized button to ShareThis button functionality.
    var element = document.getElementById("SpreadTheWord");
    var button = object.attachButton(element);