Staggering the Line
You know how you're frequently faced with setting a straight line? The question is always "How do I stagger my line so I made wedges?" The problem is always that to stagger your line and make a wedge, you have to give a wedge in return and leave a guy out.
Well, you should do this, and if you have green units to back up the line, after a round of attacks you should move the guy who was standing out and being wedged back to the line and move lesser-experienced units out to take his place. That makes your line stronger, and keeps the experienced units on the board longer.
See, in order to make the wedge you have to sacrifice a unit to make the wedge. The first unit will usually survive the first round of combat, and would normally be replaced at his death with an inexperienced unit, and your line will lose units as well that would use inexperienced reserves. So switching that guy out early is the thing to do. And you keep doing that.
So when confronted with a straight line, wondering how to make wedges, the real question is "how many reserves do I have to maintain the wedge?"