As Relative Rotation Graphs are a visualisation method there are no fixed trading rules. It is best to compare a RRG with a regular chart. A very aggressive trader may want to buy a 5-bar breakout while a more conservative trader would like to buy a 20-bar breakout.
Interpretation on RRGs is the same. A very aggressive trader may want to look for buying (relative) opportunities when securities cross into the top-left 'improving' quadrant while more conservative traders may want to wait until the security reaches the top-right 'leading' quadrant.