What is your usual strategy in stealth games?

Move past those that I reasonably can.
Subdue those that are blocking my path or patrolling areas I intend to frequently move through.
Kill anyone I can't subdue.

Basically, I like to clear a hole in their defences and just use that as a central highway into all the areas I need to get into without having to clear guys out of the way each time.

It depends on the game, though. Payday 2, for example, limits you to 4 guard kills but unlimited civilian kills (though it costs you in game currency). The maps tend to not be to big. However, there is usually a guard overseeing the cameras. Because of that, one kill is reserved for him, the other three I generally pick out depending on the map and objective. I then try to avoid any casualties, but if I run out of wrist ties or the person would be difficult to move out of the way, I'll take them out and bag their bodies.