It's not at all hard to get a good spot.
A couple of tips:
- something to sit on is nice; the bleachers are metal and can be cold - we try to remember to grab a blanket out of the stroller
- we try to either sit on an end that extends out further than the row in front of us (unobstructed view) or else we pick a seat behind short people who already look "settled." Because so many people arrive right when the show is starting, the "empty" row in front of you may not stay that way!