1) The type of news release
2) How relevant it is to the current macro-economic situation of the time
3) The instrument being traded
You can do backtests to determine some typical scenarios and average post-release movements.
Trying to trade news releases is tricky at best, more likely dangerous because of wide spreads and the possibilities getting stopped out on whippy moves that get you out at a much larger loss than you had planned for. They are seductive to try to trade because the moves can sometimes be very large.