You can use different indicators to identify a trend reversal, such as fibonacci retracementes, breaks of trendlines, etc. On the daily charts i find very usefl the break of the trendline. I will explain it with the chart:
This is a daily chart of the EUR/USD, as you can see the red line is a down trend line. You can see a lot of corrections (gray circles), and the price continues down. When the line is broken (Yellow circle) you can start looking signs to buy, it could be a fake break but you have to be prepared for a trend reversal. It is good to find any other indicator that confirms this, like a break of a 100 or 200 Moving average in the 4H chart. Dont be afraid to enter long. If the trend reverses and comes back down again, you can re enter short.
Then you have an up trend yellow line, and a couple of corrections, and finally a trend reversal. Then you have a blue line (down trend) and then a break up.
Hope that helps.
Feel free to ask any question