<form method="POST" enctype="multipart/form-data" id="fileUploadForm">
    <input type="text" name="extraField"/><br/><br/>
    <input type="file" name="files"/><br/><br/>
    <input type="file" name="files2"/><br/><br/>
    <input type="submit" value="Submit" id="btnSubmit"/>
</form>