One more tip.
By default a single shadow caster has quite weak shadow, even if darkness is cranked all the way up (specially for night scenes).
To get naturally looking dark shadow you may want to stack them up. Keep duplicating them up until shadow is dark enough.
(just tweak spacing between them as stacking can cause shadow artifacts on the ground - a z-fight)
You may also attach all casters to some dummy for easy management.
Here I have a *pyramid* of 5 spot shadow casters:


as oppose to a single caster, which leaks a lot of lights: