Experience will help of corse.
Learn the distance of your normal pace ... mine is 30".
I prefer to hang with at least 12.5' between ... that's 5 paces.
6 to 7 paces puts me at ~15-17' which is as far as I normally want to go.
As you learn the span, hugger height judgement will come naturally. A way to remember might be something like: span of 12-13' face height, 14-15 top of the head, 16-17 1 ft above the head. YMMV