Let a new plant grow for two years before harvesting any stalks and only take 1/3 of the plant on year three. After that, you can harvest rhubarb heavily, leaving the smaller stalks behind after a solid 6-8 weeks of pulling off stems for yummy pies, compote, and sorbet!
To harvest, solidly grasp the stem, twist to the side and pull to remove. Do not cut the stalks.
https://gardentherapy.ca/harvest-rhubarb/