Expert opinion. Check ordinary news sources from time to time. If you see information about increased demand for a certain company's shares or a given commodity, this is a good sign that a boom is beginning.
Expert opinion. You can use any market analysis methods you like to analyse commodities that are experiencing a boom. Unlike ordinary instruments, scenarios like these are characterised by anomalously large trends and extremely high volatility.
Expert opinion. There are plenty of examples of booms. A recent example would be cryptocurrency. Then there's the cannabis boom we're experiencing right now.