Its all too often I see images printed large and then a customer sees the odd spot of dust that was missed in post processing. Some never even notice these spots and they end up framed or even mounted for a judges eyes to scrutinise...! Having judged many competitions these pesky 'dust bunnies' are a pet hate of mine. Plain and simple... if they appear on a print then I immediately take a point off! Especially so in advanced categories where said photographer should be able to see what I can see!!!!!!
Anyway... most modern DSLRs have some form of sensor cleaning but thats generally not enough to remove the stubborn bits.... regardless at the stage where you see them on a print or on your screen its too late.... so.... a quick solution to this problem and one most people even vaguely familiar with Photoshop and layers should be able to muster up the courage to try. So the most obvious tools to get rid of these are the simple clone and heal tools which work a treat once you can see all the spots in the first place. Theres where the problem starts.... if for example you have a blue sky that gradually fades to a darker blue it becomes difficult to see the offending spots. Especially if there are a few fluffy clouds in the mix..! Simply create an adjustment layer, selecting levels as your adjustment, above your main image layer. Then take the levels adjustment and drag the black slider on the histogram and move it to the right. Your image will immediately look very contrasty and weird but the offending dust spots should now be easier to see and therefore easier to remove with the heal or clone tool. Remember to reselect your image layer before trying to clone the spots away. Because you have created an adjustment layer when you are done you can simply delete the layer and your image will return to looking normal but without said dust spots. Have a look at the screen grabs below if you are stuck.
Of course you can also remove these dust spots in Lightroom or Aperture but in general I leave that job for photoshop. I find it quicker and more precise in there. In saying that, Lightroom 5's Spot removal tool is massively better than previous versions...!