At 8:30am EST they will release inventory numbers, and note whether there was more demand in the last week or less, based on the numbers. Leading up to this even, traders tend to speculate based on a combination of factors. If prices have been high and rising, the market has likely priced in a smaller than forecast inventory. However, if prices have fallen going into the inventory report, traders may be expecting a smaller drawl than forecast.
Traders use UNG calls and puts, BOIL (bullish nat gas), KOLD (bearish natural gas) to take advantage of the volatility. Some trade both sides with a straddle in calls and puts, betting on volatility but not a direction. Others bet on a reaction in one direction using aforementioned commons or options.