I agree with Delicious.
I don't ever charge for tastings because I schedule them whenever I get a similar order to what they want. I just add more batter and save the cupcakes. They can pick them up or have the consultation then. People seem to love it. If the wedding is far enough out, sometimes I call again for another flavor I think they will like. They just pick up a box of 2-4, or a few slices of cake. That's another thing I do... make the cake they want for my next personal event and save some pieces. My way is very informal, but so far, I'm at 100% on my closing ratio.