A lot of it is experience.
Different fibers and/or different yarns need a different amount of WPI (twist per inch) depending on things such as final weight (spider web to super bulky) of yarn, the crimps per inch of the fiber you are spinning, the lock length, things like that.
A fiber with a long lock length that you are spinning bulky would need less TPI than a cob-web yarn using a short stapled fiber.
Slow down your treadling (if on wheel) or park and spin (if on spindle). Every so often stop and let the yarn try to twist back on itself. If it does (and your spinning for a plyed yarn), keep spinning the way you are. If you're spinning for a single and it twists on itself, you need to treadle slower OR adjust the take up on the bobbin faster so you don't get as much twist in the yarn.
As an aside ...ABATE of CO, eh? Very cool. "Back in the day" (early to mid 80's) I helped set up two chapters of ABATE in eastern IA. At the state level, I was one of the folks that helped set up the petition for a house & senate bill to charge $1 for a motorcycle learner's permit and that money go to fund Motorcycle Safety Courses in the state. (And was the first woman safety course instructor)
Over 20 years later, my oldest son (20) bought his first bike ('05 Super Glide) and went through the MC Safety Course.