Waves one, three and five advance; waves two and four correct. Wave three is usually the longest and strongest and is never the shortest of the three, which is one of the theory's few unbreakable rules.
Practitioners look for wave three to show displacement and heavy volume, and for wave five to show weaker momentum than wave three, often producing a divergence on rsi or macd. That momentum divergence is the part of the framework that overlaps most with conventional analysis.
Identifying which wave you are in while it is happening is the hard part. Counts routinely get revised, and a supposed wave three frequently turns out to have been wave one of something else. Use the structure for context, not for precise entries.
Related: corrective-wave, elliott-wave-theory, wave-extension, displacement, divergence