That's one reason I suggest just trying to make sure your honest feelings come through. In the example I used:

One friend of mine was explaining a counterintuitive study in a fairly matter of fact way, but it was a lot more enjoyable and memorable to hear about if she shared her surprise at how it turned out. A lot of the time, it's simplest to just make sure you're letting your honest reactions to what you're saying come across.

Her even affect was actually camouflaging the content. People had to work harder to notice that the result was surprising because she was communicating that fact exclusively through language and not through intonation.