Nope, it isn't first come, first serve. I am not sure how crowded it has been lately, but here is the policy:
Lottery: 25 tickets will be sold for each performance at $25 each. Effective September 20, 2005, the discounted, same-day lottery tickets will be for seats in the first row of the orchestra. The lottery** takes place daily in front of the Neil Simon theatre. Each person may enter only one name into the lottery. The individual whose name has been entered must be present to purchase tickets (2 tickets per person; cash only; photo ID required).
Lottery sign up begins three hours before curtain. There is no need to arrive earlier.
http://www.talkinbroadway.com/boards/index.php?rush=show Good luck!
"We like to snark around here. Sometimes we actually talk about theater...but we try not to let that get in our way." - dramamama611