I'm an economist and that's basically what I do for a living. There is no easy answer to your question. A number of questions must be answered first:
1) What are the prices? Are they commodity prices, stock prices, .....?
2) When you say "predict their outcome" do you mean predict the future? What will those prices be tomorrow, next week, next month?
3) Of course, one can never predict anything "accurately" into the future but to even come close always requires some additional information. For example, to predict commodity prices you might need information on interest rate changes, exchange rate changes, etc. Then you proceed to some sort of model. That's what economists do.
4) Following up on point 3) then, why do you want to do this? If it is just for curiosity then playing around with Excel or a statistical package may give you an idea about how forecasting is done. There are many approaches and programs. But if it is to make money in the stock market or in a commodity then BEWARE. Any form of mechanical, mathematical or statistical forecasting is very unlikely to do any better than just plain old experience.