An extremely aggressive method is to simply place a limit order at the trend line when the price gets close to it. However, this can be problematic because it is a rather aggressive strategy as the price level of the line shifts slightly with every unit of time. Additionally, sometimes the price comes very close to the trend line and reverses without ever quite touching it. For these reasons, it is usually a better idea to wait for a reversal to be confirmed by Japanese candlestick analysis / price action analysis to identify the turn, not entering the trade until the turn happens.
How can you identify the turn? If the price moves towards and rejects the trend line very quickly and strongly, a single turning candlestick might be enough confirmation. If the price is moving slowly, waiting for a compound candlestick formation of maybe 5 candles is usually a better method.
One thing which can help increase the probability of any reversal trade is checking that the price is making more significant higher lows than highs (for a bearish trade) or vice versa (for a bullish trade).
Finally, it helps to know when to give up – in other words, when to conclude that the turn is not going to happen. Again, if there are many consecutive or near-consecutive candles that violate the trend line and don’t react one way or the other – say between 5 and 10 candles – it is usually obvious that there is no good trading opportunity to be had.