kneading

When the dough starts fighting back and feeling tough, you should just set it aside and let it rest for 10 minutes or so. The  toughness is a sign the gluten is tightening up too fast, and leaving it alone for a while will let it relax. (This also works with pie crust, a fact I learned too late to save me from years of bad crusts.) 

With lean French breads, you can get by with little actual kneading, if you give it a long autolyse (or, in English, let it rest) after you first mix the ingredients, then with maybe a couple of minutes of kneading, a few stretch-and-folds and a long, slow, cool ferment, the dough will develop quite well. It does take some trial and error to figure out how much handling is enough, regardless of the method you're using.

"I am not a cook. But I am sorta cooky."

The stiffening of the dough can also be a sign that you've kneaded enough, if the texture of the dough is otherwise smooth (not lumpy).  Time to form it in a ball, put it in your greased container, and let it have it's first rise.

For some recipes, salt is added after the kneading has started.  I've notice the dough stiffens when the salt is mixed in...salt also tightens the gluten but is very important in terms of taste and balancing the proteins that form the texture of wheat breads.

Windi