If the high is a better than previous high and on good volume then it is likely to be a new leg up and so buying in with a tightish stop would be a good bet. The reverse for new lows. i find fibbonacci and the RSI good tools to indicate highs and lows on all timeframes.
You buy low and sell high, its obvious but not easy to do. You are actually wired to sell when market falls and buy when it is rising. I have lost most of my money this way.