Best fencing question so far.

I was told to stretch until the little folded notches in the wire just begin to straighten out.  You don't want to stretch the wire completely until the notches are gone, but as you notice the notches bent into the wire begin to move, you quit stretching.  If you are going on hills or uneven ground, you have to travel the length of wire to make sure it is not getting caught on the ground, lifting it up once and a while.  If you are going through a valley, it is trickier, you have to fasten the bottom wire to make sure it will go down into the valley.

All we ever used to stretch woven wire was the boards and bolts, homemade, do not need anything fancy.  Cut two boards the length of the wires height, mark a place where a bolt would go through between the wires, and drill the holes.  Make the holes small enough for the bolts to be forced through the wood when hammering, that way you will always have the bolts stuck on the board when you take off the nuts after stretching.  Put the boards beyond the corner post and stretch, then use wire staples on the corner and second post before releasing the tension on the wire.  Cut the wire long enough that it will wrap around the second post, and tie the long wires left back to the face of the fence, to hold it better.

My FIL and I put up a lot of fence, much of it still standing after many years.