As an audience member purchasing tickets for a show, we are all guilty of trying to find the seat that we think is the best one. Is this the best seat in the house? Technically, if we are doing our job right as creators and artists, every seat should be a good seat. The thing that makes a seat the best one is being able to see, and because of that, sight lines are one of the most important, and I think, overlooked parts of the production.
Too many times, I have gone to a production and had to crank my neck to see what was going on. Inexperienced actors are upstaging themselves so all I see, are booties. This happens because often, directors only block from the center stage view. I know I have been guilty of it in my earlier directing days, but I learned real quick when I sat in the booth that the view of the production from center stage is entirely different from a balcony or stage right seating section. As directors, we should aim to make every part of our blocking an opportunity to portray something interesting about characters and dynamics that can be relayed from any seat in the house.
So how do you do it? I'm not saying it's easy; it takes a lot of trial and error. The first thing that will help remedy the booty problem is teaching your actors how to cheat out. Sometimes rehearsals are done in smaller spaces instead of the actual performance space, so making sure your actors are aware of how their bodies are shaped on stage is important. Keeping actors aware of what an audience might be experiencing in this scene is important for them to make sure they are portraying what you want as a director.
Secondly, you have been preparing for this production for a while, so you know the space and what obstacles you may encounter. Thus, you should block with sight line problems in mind. If you know, there is a sight line problem at a certain height keep platforms low enough. If you know that a person sitting all the way stage left can see into the wings, adjust accordingly. The goal is to give your audience an amazing theatrical experience and showing them the magic of backstage or breaking their focus by having to move around in their seat trying to see is going to ruin that, no matter how good the acting is. Now, don't get me wrong; some blocking requires backs to audiences, and I love a good dynamic tension on stage, just make sure the booty is intentional and not a mistake.
Lastly, the best way to test the sight line theory is by merely sitting in different spots during a run of the production or during blocking scenes. You should not direct for the one seat center stage, because hopefully, your audiences will be for an entire room. You are doing your production a disservice if you don't think about the advantages of blocking from different angles and creating an experience for every seat. It's also a disservice to your actors because you're teaching them to ignore the sides of the audience as if only the front and center matters. A good actor and director know how to think about the view of the audience and strive to make sure you are creating for every person.