An early point in Blighted Quiver helps harass enemy champions and get killing blows on minions.
During short range fights it's sometimes best to fire Piercing Arrow quickly, rather than charging it to full power.
Try to take advantage of Piercing Arrow's very long range to snipe at enemy champions before a fight or as they're trying to flee.
If you are affected by Blight, Varus' abilities will deal extra damage to you.
When he gets a kill or assist, Varus temporarily gains Attack Speed and is much more dangerous.
You'll get bound in place if a tendril from Varus' ultimate, Chain of Corruption, reaches you. You can cause the tendril to die however by running far enough away from it.