First, thanks for the reply 
See, I don't know how x(
I feel absolutely ignorant, but once I say:
Servo serv;
serv.attach(9);
serv.write(180);
I don't know how to stop the servo. It just keeps spinning.
I don't want to guess where the value of the pot is and try saying serv.write(90), because I don't want the servo to waste energy by spinning slowly to try to satisfy some fraction of a degree difference.