Here's a a few tips when using neural networks.
1) standardise the inputs by using the natural log of lagged returns (eg take the log of the difference in closing prices over x bars)
2) look for correlations between a target variable of AT LEAST 50 bars in the future, and inputs using lagged returns covering the past 50-250 bars
3) use intermarkets as the primary source of inputs
4) keep the number of inputs below 7-8 (as few as possible)
5) do not use more than 1 hidden layer
6) build several networks and use emsembles
7) do not try and predict price as the target variable - rather predict the log return of price over the next x days, or something like the rsi.
8) stay away from predicting moving averages - they are easy to predict and utterly useless in real trading (one particular software vendor uses predictions of moving averages and i know from bitter experience its a pointless exercise)
9) before building a network do seperate analysis on correlations
I have reserached neural nets for some time and have had some success - particularly with forex. (e.g over 90% directional accuracy at predicting direction over the next 50 bars on out of sample and live trading). Its not easy, and every market behaves differently, so no holy grail.
happy trading.