A trader can spot a rally by using technical indicators like oscillators, which can help identify overbought assets, which are one of the main drivers of market rallies.

However, the length of a rally can be relative depending on the timescale used by a trader. A day trader, for example, may see a rally in the first 30 minutes of a market opening if beneficial market news has broken during the night.

Position traders, on the other hand, may require a sustained upward movement over a period of days or weeks in order to consider a period of upward movement a rally.

Traders identify a rally as a sustained upward movement in the price of an asset, often driven by increased demand or positive market sentiment. Key indicators include:

1. Price Patterns: A series of higher highs and higher lows suggests upward momentum.
2. Volume Increase: Rising prices accompanied by higher trading volume confirm strong interest.
3. Technical Indicators: Tools like moving averages, RSI (Relative Strength Index), and MACD (Moving Average Convergence Divergence) can signal a rally when showing bullish trends.
4. News and Events: Positive earnings reports, economic data, or announcements can spark rallies.
5. Breakout Levels: Surpassing significant resistance levels often triggers rallies.

By combining these signals, traders evaluate the strength and sustainability of a rally, aiding decision-making.