I am relatively new to bread making, so I am often uncertain about kneading dough.

I've been told that if I knead the dough too much, the final product will come out dense.

But I've also been told that in order to get air into the dough, I should knead the dough

pretty thoroughly.

For example, making baguettes. I guess I'm supposed to knead the dough quite a bit to get

those holes that baguettes are known for. 

So I guess my question is... How much is too much?