In general, it depends on your timeframe: longer term stuff you are going to need to understand fundamentals. Short term trading (5 mins and less, if its a good trade), you are going to have to understand news, technical analysis and flow, watching orders coming into the market. Identifying when a spread is ranging and when its trending is key. Typically, looking at bollinger bands: using a moving average as a poor man's regression. The bands are the standard deviation, an expression of how far it is from fair value. Fundamentals are also important in short time frames, but they can be affected by market position. For example, after a number, its possible to get profit taking sending the market in the opposite direction to what you would expect from fundamentals. Probably best to avoid trading over the inventory numbers, instead learning how irrational the moves can be. Rather than trying to knock the ball out of the park, calling an entire move, its better to have lots of little profits steadily building your P&L.