Pull your bottom wire after setting your ends and corners to use as a straight line. We then stretch all the other wires top down. Although that really doesn't matter...but always tie or staple from top down
I put fence in one strand at a time because of labor/equipment availability. I string first strand to use as straight line for post and then start from the bottom and work my way up. It seems easier to keep wire spacing even throughout. the only advantage of starting on top that I can think of is that the corner post are more likely to move the higher you go; therefor starting on top would help insure that the lower wires stay tight as you pull the other wires tight. If you do a good job of installing corner and brace post, you should have the same result whether you start on top or bottom.