Bollinger Bands (price touches lower band = oversold). RSI < 30. Stochastic < 20. Z-score: |price - MA20| / SD > 2.
Buy when: price touches Bollinger Lower + RSI < 30 + bullish reversal candle (Hammer, Engulfing). Stop loss: below support/swing low.
TP at MA20 (mean). Or Bollinger Upper. Or R:R 1:2. Don't be greedy — mean reversion = small profits + high win rate.
Strong bear market: price can be "oversold" and continue falling 50%. Mean reversion fails in strong trends.
Advanced version: long underperformer vs short outperformer in same sector. Beta-neutral, less market risk.