How much cleavage is okay to show on a second date?

I see this question is in the category of "teen dating", so I'm going to be old fashioned and say that the amount of cleavage shown on the second date should be the exact amount that you wouldn't mind your father catching you showing!

Now really, slow down! A second date? Regardless as to what the movies say is cool, you may go slower then you are. It's a bit early to try to entice him with cleavage! Learn about him and let him learn about you, there is all the time in the world for cleavage!

And remember, there are reasons why fathers are concerned about what cleavage their daughters show. It's because dads used to be teenage boys, and are well aware of what teenage boys are about! So be careful about trying to entice one of them!

Now if this is being asked by an 18 or 19 year old, then you may still be moderate. Showing too much cleavage may in some ways be pleasant for a guy, but most guys very quickly learn that the more cleavage a girl shows, the more...uh..."experienced" she is. And most guys aren't interested in that. Well, at least not for the long term.