My rosemary plant went from a spindly little sprig to a big woody bush
(14" across/high) over the course of the summer, despite frequent
trimming for various culinary exercises.

I have dug it up and put it into a pot with some of the soil from its
garden bed.

What is the best way to ensure a good watering level? The bed it was
in was well-drained, and we rarely watered the garden this year thanks
to frequent-enough rains. Inside, the atmosphere is going to be a lot
drier, and I wonder if there are any easy tips on making sure the
plant gets the right amount of water.

Any ideas?

Mark