When to sell a stock

It does everytime as I am sure it happens to many of us. We can never predict the highest point a stock can reach and often sell at our target price or when we want to cut loss. There are a few occasions and it happened to me that after I sold off a particular stock, the very next moment, the stock was called for a trading halt and good news came out. Unless we know some insider information, else usually when the stock we are holding make some money, there is a very high tendency that we would sell the stock to lock in some profit. But again, no regrets in doing so.