Use Flash and R together to catch opponents by surprise. Have the ball on top of your head then R and right before the Shockwave goes off Flash onto your target then Q W AA E instantly.
To chase someone down for a kill Flash then instantly Q AA and W as soon as your Q lands.
Surprise Flash kill your opponent by placing your Q down and then walking outside your Q cast range. When your opponent steps up Flash and instantly Q W AA them.
To All In Q in front of your target then instantly R W, line your E up for return damage then instantly AA.
To maximise your damage you can delay your R. Q W your opponent then ult them once they reach the max range and E AA them until your next Q.
To sneakily ultimate someone Q towards your target, wait for your next Q cooldown, then right as it comes up ult your target and instantly Q W E.
Your most basic trade is Q and instantly W before it lands.
For a more lengthy trade Q and instantly AA, then W E as soon as it lands.