There is also software available that will place your bids for you at the end of the auction. Ebay also allows you to place a maximum bid for an item. Others have to bid up to your bid to win. If no one matches your highest bid, You win the item increments (could be pennies or dollars depending on the price of the item) over their last bid.
So I say... the best strategy is to place your maximum bid and do not look again until the end of the auction. Otherwise, you get caught up in winning and do not pay attention to what you are spending.