Wheelbuilding setup

How do you know what is the 'right' spoke tension? This is my main problem when I've ever had to rebuild/true wheels. In the past I've put on too much tension and spokes *have *snapped...

i done it by feel
i had a set done by a shop and i just felt the tension on them and built my wheels near enough the same (tension wise)
only time will tell if im any good at building wheels

Seem to be a lot of people only building front wheels on here.

ive built a rear or 2
i think rear are harder because they take most of your weight so have to be built spot on
thats my opinion anyway