Things that really convince me are comparisons with already existing stuff. Show what the problems are with an example program like c++ or java and show how d resolves the issue. Be careful though, one of the first things that put me off is when I feel it's too biased and they only show possitive points. "if something is too good to be true it usually is"

show them how open D is to multiple programming paradigms and how well it is integrated in the language. 
show them the shining points of D like it's array's or CTFE.
show how beautifully the syntax looks compared to c++.
Show them that with D you can write high level but go low level very easily if you need it.

Just playing with ideas here :)