So how should we react to each of those trends? How long should we wait until it forms a trend (for example: a seemingly downward trend may actually be a sideway over time).?

Hi there! Long answer short, but one way you can ascertain is by looking at the historical price and determining whats the long term trend.

Bear in mind that trends are categorised into 3 types: long term, intermediate and short term. Typically, short-term trend lasts a few days to weeks; intermediate-term trend lasts weeks to months; long-term trend lasts months to years.

Hence, to not make the mistake of thinking that a seemingly downward trend may be actually a sideway movement (aka consolidation), you could look at the long term trend to get a better understanding of the stock price movement.