The beginning is when it breaks to new market highs. As the trend matures and progresses, it will keep breaking out to new market highs.
A good breakout is when there has been testing on the resistance, and the resistance has held a few times in the past.
If you want to get in the action (the big trends), then buying when a breakout happens is a must for currency trading,
and this is a good way to make profitable trades.