The third technique is just like the first, but with an added twist. I sometimes favor using a squirrel call when I haven't eyed many squirrels in a spot that I know is ideal. Squirrels are extremely vocal animals, and you'll often hear more than one chattering at a time. A chatter call will often get others chattering and reveal locations. If this is the case, put on a stalk.
Chances are a curious squirrel is coming in to investigate.
This is indeed a matter of personal preference, but I will defend my claim. Pellets can be a pain to keep removing and there is no need to damage more meat than need be. Second, a shotgun blast will alert the whole woods to your presence. Though a .22 can sound loud in the quiet woods, the effects will not be nearly as serious. I've shot many consecutive squirrels with a .22, but getting more than one at a time with a shotgun is rare.