how to identify trend

you can use churn prediction/method. Or you may based it on sample data like getting the increase/decrease percentage in a given time they you can predict average output.

To Identify the trend you can choose to see at different Time Frame. In the case of Forex you can see on Time Frame 4 Hour, 8 hour, Daily. If the three shown us the same direction then we can sure that the trend is to that way (up/down). Another way is by using Fibonacci Formula or Elliot Wave. Choose one or combine both :D