Quote from DrPepper:
The highest probability trades are in the direction of the trend. If you are using MACD to determine the trend, then you want to only go long when MACD is above it's moving average and short when MACD is below it's moving average. Therfore, waiting for MACD to signal a direction is your first step.
However, in an uptrend, rather than "chasing the market" by buying a new high, it is often best to wait for a retracement to "buy on weakness". In an uptrend, when %R is less than 20-30%, that would indicate that the market is "oversold" and that it is a retracement worthy of buying. In an uptrend, oscillators like %R tend to stay oversold for brief periods of time. There is no guarantee that price will not continue to go down, so stop losses are necessary.
In an uptrend, %R and other oscillators tend to stay overbought at the top end of the range for extended periods. Therefore, using oscillators to signal countertrend trades, even with bearish divergence, is quite risky.
See the attached chart illustrating the above explanations.