For services the best thing to do is to start at what seems to be high (but not so outrageous that people label you a kook) and scale back as needed. Nobody will complain if next month's bill is smaller than this month's.

For actual shipped products things are much more difficult, if you price high and people buy but not enough people buy and you then lower the price "too soon", the early adopters will feel understandably pissed. See: Nintendo 3DS.