Opening Night Jitters

So, being a novice at this whole"giving birth" thing, I am a little concerned about the timing of it all. At work, one of my coworkers has been asking me if she needs to get some hot water bottles and an emergency kit ready. While I don't think hot water bottles have been used in birthing since 1908, she has a point about being prepared. Where is the line, I wonder, between siting and just waiting for baby to come, and keeping yourself busy but going into labor on your desk at work? Not having been through this I have like zero concept of if I will even KNOW I am in labor and if I will be in the type of discomfort that you just don't want your coworkers to see you in. Can you do what you do for opening night nerves and just do shot and some breathing exercises? Hmmmmm . . . Alright Sue, maybe you SHOULD get those hot water bottles ready . . . and clear off a spot on Teniqua's desk!