How much you should bid on a house depends completely on the local market and how well the seller did in setting a realistic list price. After the recent bursting of the real estate bubble, many sellers overpriced their houses, unable to believe that the widely reported drops in home values included their house, too! In such a situation, you could safely underbid.
However, in a hot market -- or even in a hot neighborhood in the middle of a cold market (they do exist) -- the list price might be just a starting point, and you'll be expected to offer a higher price if you want to beat out the competition. Underbidding in such a situation would be a complete waste of your (and your real estate agent's) time, and the seller would be unlikely to make you a counteroffer.
The key is to develop a good understanding of the market and how much a particular house is really worth, using the advice in Nolo's article Making an Offer to Buy a House.