Volume is one of the best indicator of the trend. Think of the price as a constant war between buyers and seller: Buyers are longing the market, as they feel that the price of the stock is undervalued and that it will apprecate in the future. On the other hand, Sellers are shorting the market, as they feel that the price of the stock is overvalued, and will fall in the future. This constant war between buyers and sellers will thus dictate the price- if there are many buyers, and few sellers, demand is more than supply and prices will go up, as people want to get into this presumed undervalued stock. On the other hand, the converse hold true- many sellers and few buyers would meant supply is more than demand, and that prices will go down, as people want to get out of the presumed overvalued stock. When would be a good time to buy the stock? Volume then, would be the key indicator of price as it would reflect the trend- bullish(appreciating) or bearish(deppreciating), and can signify trend reversal- the bulls or bears may be becoming exhausted, and the other party would take over. Ultimately, it depends on your mindset as an investor, and how you view the value of the stock. If you think that it is overvalued, then sell it. If you think that said stock is undervalued, then buy it. Ideally, volume would help you to guide your decision.