Here are some of the key criteria and indicators used to judge a market top:
Price and Volume Indicators:
On-Balance Volume (OBV),Moving Averages (MAs),Relative Strength Index (RSI),Bollinger Bands
Market Breadth Indicators
Advance/Decline Line,McClellan Oscillator
Volatility and Sentiment Indicators
VIX Index (CBOE Volatility Index),Put/Call Ratio