Assuming you're running KS 8 or newer, the easiest (not necessarily the best) way to do this would be to use the "Spots" texture node on a plane with Solid Glass material applied (play with the density, scale, levels, falloff, distortion, etc., to get a realistic degree of randomness/variety to the spots) and use that node as a displacement map (and bump). You'll have to invert the black/white so the dots are white, background black and play with your displacement settings (i.e., more/smaller triangles, probably lower-than-default height, etc.). Once it looks nice, drag that same spots node over to the opacity channel which will remove the rest of the plane and leave only the droplets behind. Then make a duplicate plane for your base glass material and make it a slightly frosted material (i'd use a map to control the frost so it's not universal, you could even play with using the same spots map/inverse) to fog only areas that don't have drops. And I'd even do a second pass of spots for the fine mist in between larger droplets as well.. It's a lot of fun to play around with.
Outside of that, the "better" approach would be to get your hands on RealFlow or Houdini and run a particle simulation with surface tension/friction, etc. which would make the droplets have a more interesting falloff and realism upon closer examination. Just depends on how far you want to take it. With RealFlow, you could obviously make the droples run down the glass at random, if you were to do an animation of any sort..
Hope it helps.
