Possible Clues:

• Words before an attempt
• Words of daring, say, embraced by champions
• Gee/horse? Anyway, we're off!
• Comment before an attempt
• Daring person's cry
• Words before a bungee jump, perhaps
• In there go especially fast and let us see what happens
• This is the exit, for a start
• ___ nothing
• ''I'm gonna try it now . . .''