If a blower doesn't do the trick, I use a rubber spatula trimmed to a square edge. A piece of a lint-free wipe (courtesy of the lab I work in) wrapped around it and pure methanol (lab courtesy again) as the liquid. Many folks use Pec Pads or some such. I'm leaving details out because this being CR, you'll hear many opinions and gnashing of teeth. As someone else posted, you'll find a dozen guides on the internet for sensor cleaning. Read/watch them and figure out what you want to try and practice on a piece of glass. Kinda like changing oil and tuneups - learn to do it yourself and you'll both save money and know it was done right. Always always always use a blower FIRST!! Just don't use canned air. In a past life I made my living working on optics, so I have my methods and I'm both experienced and comfortable with them. I'm a fan of that piezo-electric-vibrator thingy built into the sensors now, it knocks the boulders off the sensor and minimizes the potential to scratch the glass when cleaning. I frequently change out cameras/lenses/telescopes in the field, so my sensors tend to get dirty. I'd go broke sending them in for cleaning.