Now, let's get to the nitty-gritty - how do you actually prune your green beans? It's not rocket science, but you do need to know a few basics. First, you'll want to wait until your plant is around 6-8 inches tall, with a few sets of leaves on it.
Pruning 101: How to Prune Plants for Maximum Success in the Vegetable
Then, using a pair of clean and sharp pruning shears, you'll want to cut off the top growth of your plant, just above a node (that's where a leaf meets the stem). This will help your plant branch out and produce more beans. And, don't worry if it seems a bit counterintuitive - trust us, it works!
It's similar to when you're trying to get a new job - you need to highlight your best qualities, and downplay your weaknesses. By pruning your green beans, you're helping your plant showcase its best features, and hide its not-so-great ones.
Green Beans Plants Pruning at Oralia Raby blog