Should I water before the soil dries out completely or wait until it is dry?
I try to wait until the top inch or so....excuse me, 2.5cm?....is dry before watering.
Alas, my work schedule makes my watering more of a timed scheduled thing, than accurate care, as it should be.....That's one reason why I like to use mostly inorganic substrates, which can "make over-watering impossible"...I agree with this notion as long as the container is one that doesn't hold a bunch water...
For example...
(Poor picture, but its the only one have at the moment) This juniper is in a heavy freeze proof flower pot from Home Depot, or an equivalent...its round and tapered like a funnel....and it has 4 one inch....sorry, 2.5cm?....drainage holes.
It drains like a champ!
I have a few of my trees in the exact same pots... Obviously this is a training pot...and once the trees are ready for true bonsai pots, they'll have a suitable rootball to do so.