Basically, I have 3 or 4 occupations.
-Proles (for lack of imagination) are assigned almost every single labor that doesn't require skill and also masonry and engraving and mechanics. Tanning, butchery, hauling, building walls, smoothing floors, resetting traps and all those odd-job labors. These guys are all in the militia as well.
-Specialists, which are basically proles with some of the busy work disabled, but have whatever moderate or low-demand specialty they are good at enabled, plus wood cutting or mining. This field mostly exists so I don't try to put miners and woodcutters into the milita and I end up with moderately skilled immigrants that are useful enough to do something other then drudgery all the time.
-Artisans, which have all labors disabled except the one high-demand profession they are good at, like skilled masons, carpenters, weaponsmiths, ect. When my fort is smoothed out, the best engraving proles get promoted to this. They are in the milita so they'll carry arms to protect themselves, but are really too important and busy to be doing training.
-Full time soldiers
So, I rarely have idling dwarves, there is always something to keep them busy, mostly artisans I don't have much use for at the moment are the ones hanging out being bored.