The ideal first rule is to find voice actors who can sing, has soaring popularity and big racks to voice the main characters. The second one is to avoid creating original anime, because if the ideas to be presented are all horribly mashed together, then it is doomed. The third is to find production staff with a motivation more than "just because".
Yet, look where we are. Being both an original anime, and has mostly not-so-popular voice actors to back up the main characters, Shirobako colorfully takes off to the sky. It defies the very rules that it sets, the challenges that it adds and trample them one by one. All through the perspective of the characters inside the story world. And, there are tons of them.
Annoying ones, irresponsible ones, and lazy ones. But most importantly, are the ones that are willing to go the extra mile, to hold the team together, to make the sound effects a bit better, to make the sky a bit sadder, to do just a few more key frames, to give one piece of advice, to spend a few more nights and ultimately, to dream.
To make a great anime.
Shirobako is a prime example that only one's own efforts can move oneself. It's never easy continuing something without credits, and only criticism. But little by little, you're gonna make it. Because everyone's been through it. Made stronger by it. And these lessons, they never stop emerging and igniting the fire inside others. To inspire, and to support.
Overall, Shirobako is far from cute girl doing cute things in anime industry. No. It's the struggles they face, the surprises they dread, and the taste of teamwork comes to a satisfying conclusion that makes up the story. They dream, they do and they keep pushing forward however bitter disappointment tastes. The four of them, and her. Moving forward, little by little.
One step closer to their dream.
