Stan Weinstein's book 'Secrets for Profiting in Bull and Bear Markets' is without doubt one of the classics books traders read.
Weinstein said that at any one point in time, a stock (or an index) will be in one of four market "stages": Stage 1 the Basing Area (also known as consolidation or accumulation phase) Stage 2 the Advancing Stage Stage 3 the Top Area (also known as the distribution phase), or Stage 4 the Declining Stage
One of the concepts from the book that became classic is the definition of the four stages a stock can be in. These stages basically classify the different periods in the lifetime of a stock. An important thing to understand is that Weinstein uses weekly charts and identifies the current stage based on the direction on the 30 week moving average.
This script plots the 30 week moving average and the 150 day moving average.