Every quarter we go through "Earnings season". Each company comes public with their prior quarter's earnings and analysts try and guess what they think the earnings should have been. If all goes well and the company posts earnings that match or beat analysts' expectations they are usually rewarded. Miss the expectations of analysts and its usually a bad sign for share performance. The problem is that when the earnings are reported the stock usually makes a sudden move that is almost impossible to catch so how do you know which moves are good ones that you can chase?
Well to start you want to look for a "new move". What this means is that the earnings gap (or move from the earnings announcement) has started a movement in a new direction. This could be that the stock was trending lower for a few weeks and the earnings move has caused a strong reversal day. It is in this case that more types of investors are likely to get excited about this. Also it is unlikely that those who have held losing positions during the downtrend will be able to put enough selling pressure on the new buyers to push the stock back lower. They may also even consider holding their positions now that it is moving back in their favor which would subtract from any selling pressure.
Another move you may consider chasing is a new breakout. When a stock is directionless for a period of time it just means that traders have no reason to buy or sell. There may be a lack of news or it could be that people are just waiting for the earnings to come out. When there is a strong move above the directionless move it is common for traders to think that this is a new move and you will likely see some strong buying as the days go on. This type of move also attracts the day traders and short term traders as well so it just adds to the momentum.
Not all earnings moves are good ones to get in but hopefully this helps you hone in on those that may have a greater chance of continuing in your direction.