Learn how to do the windowpane test for dough. This quick and easy trick will tell you if you've kneaded your dough enough by testing the dough's strength and elasticity.
Follow your recipe instructions to make the dough. Knead either by hand or in a stand mixer.
Once your dough has come together and no longer feels sticky, pull off a piece of dough about the size of a golf ball.
Flatten it between your palms as if you are making a tiny (and adorable) pizza or flatbread.
Hold the dough and gently stretch it in opposite directions to stretch the middle of the dough. You are checking to see if the dough can be stretch thin enough, without tearing, to see light pass through.
If light can pass through without the dough tearing, you are finished kneading. Move to the next step in your recipe.
If the dough tears, continue kneading for a minute or two. Then, try the windowpane test again. Continue this until your dough can stretch thin enough for light to pass through (aka "achieves the windowpane").
Notes
Sometimes, I do the windowpane test without tearing off a small piece. But this is usually because I am 99.9% confident that the dough is ready. And I am also just checking the general elasticity of the dough. You can try this, but I recommend using a small piece of dough until you are really familiar with dough and gluten development.