Another of the popular miss-conceptions is that militias were a shambolic, rag tag creation. This view stems mostly from things written in the 1830s when, it must be admitted, the institution was past it's "sell-buy" date. It's probably an exaggeration to apply that to the period just before and just after the War of 1812. Training days were taken seriously in many communities. I've a couple of militia order books that more than support that view. It also must be seen that there were two types of militia, the enrolled militia (which everyone was required to belong to) and the volunteer militia. The volunteer companies were formed by men who took their militia duties very seriously and created specialized units...much like volunteer fire departments today.
Volunteer companies frequently purchased matching sets of arms. They also tended to adopt the style of elite units (which they were) so we often find them designated as light infantry and riflemen. All of the rifle companies were volunteers. Also, it was never intended that the militia would be embodied as a whole. It was a nation-wide basic training program. In time of war provisional units would be raised calling on the men who had already received their training in the militia. This approach goes back to the Seven Years War and was a long established practice. In fact,it rarely happened but only in the case of actual invasion would it have been considered practical to embody the entire militia.
It doesn't take much imagination to appreciate the devastating economic effect of calling up, for any length of time, virtually the entire male population of a mainly agricultural society. As it was, the Massachusetts militia manned a number of coastal forts, usually for two weeks at a time when they were relieved by another unit. We've no reason to assume that those who went were all of the members of a particular unit either.
All of this subject deserves much more study based on primary documents, especially since the subject is badly clouded by folklore and critical statements by people who resented having to do militia service.