Try to put your Q into minions if they are next to champions, and there is also a mechanic where you cast your W before the q lands on championso you root them really quick

With the W you have to preshot where they are going (if they are able to move)

Little mechanic you can W flash : if you W and then flash the W is going to be casted where you were before the flash, it helps you to escape(with style) or to dodge spells while rooting an enemy

Place your traps into strategic areas like the river to prevent a gank or in bushes to have vision and punish a little rat trying to surprise you so they're slowed, you root them and you deal a lot of damage with your supp.

When you enter in your ult if no one ccan attack you while you're in you can take you time, you have 10 seconds, enemies will try to sidestep your bullets so wait and shoot at the good moment, if they try instead to get out of your ult, shoot infront of their way.