How good?

Be so good they can’t ignore you.

Said during an interview on the Charlie Rose show after being asked his advice for aspiring performers:

Nobody ever takes note of [my advice], because it’s not the answer they wanted to hear. What they want to hear is, “Here’s how you get an agent, here’s how you write a script,” … but I always say, “Be so good they can’t ignore you.'”

~ Steve Martin