I use a soft chamois leather cloth and blower (a blower brush with the brush removed). I've heard that the 'lens pen' is good but never used it as I'm happy with the above. The blower brush is pretty effective most of the time and I try to keep touching the front element to a minimum.
The chamois needs washing in weak detergent (and copious rinsing) every now and then to prevent a build of grease. I keep it in a ziplock bag that I change when I clean it.