Well, if you really feel you need something special for JQM, there's Codiqa, being flogged on the JQM homepage. I haven't tried it - I haven't been a fan of WYSIWYG webpage design - I think Dreamweaver (or, rather, developers and designers relying on Dreamweaver as a crutch and avoiding learning HTML/CSS/JS) is responsible for most of the bad web sites out there. ;)
Other than that, use any tools you would use for any HTML/CSS/Javascript. Most especially, learn to use a desktop browser debugging tool like Firebug or Web Inspector.