You can tell when to turn pancakes over to fry the other side by looking for bubbles that form across the entire surface of the pancake and the edges should begin setting.
When you see any bubbles that are forming and also popping across the entire surface of the pancake and the edges of your pancakes are starting to set, it means the the bottom of the pancake is golden brown and cooked enough not to stick to the pan and they are ready to flip to fry the other side.
You can confirm that the pancake is ready to flip, by gently lifting the edge and if it does lift easily with a spatula, then the pancake is ready to flip to fry the other side.
When the edges of the pancake start to look cooked, you should then lift one side to check the color of the side of the pancake faced down and if it does look cooked then you can flip the pancake.
I always will wait until I see the bubbles appear on the surface of the pancake and then flip it to fry the other side.
When cooking pancakes you fry the pancakes one each side for around 2 minutes before they need flipped.
Cook one side for around 2 minutes and then use a spatula to turn the pancake over and cook the other side for another 2 minutes.
Common mistakes when making pancakes are over mixing the pancake batter, not resting the pancake batter, not starting with a hot enough pan, setting the heat too high and flipping the pancakes too soon and too often.