It's first read - the first time the director, stage manager and actors get together and just sit around a table and read the script. It's the first time you hear all the actors voices, the first time you start to get a sense of what this cast and this director are about to make of this script.
First judgements are made. You try not to, but you can't help it. Wow. She's really good. Jeez. He's already got the makings of his character. Uh-oh. That guy's going to need some work.
And you wonder what they think of you? Did they hear how you just nailed that last line? You hope they don't hear the flaws in your British accent. It's early in the process. Are you throwing out too much too early? Or too little? Hold back? Open up?
Let go. It's first read.