During the laning phase I play fairly passive and focus on last hitting minions and using my Q to constantly poke the enemy champion when possible. I take a point in pool at level 2 in case the enemy jungle decides to gank mid early and also to counter the enemy champion deciding to go balls deep and use their entire combo with flash/ignite. I tend to not use my E early game that much as it drains a lot of health and your Q doesn't heal you for that much yet. Once you get your core items like hextech/Will of the Ancients or spirit visage it is easier to spam your E to farm and harass as your heal will be healing you for ridiculous amounts. Once I hit 6 I try to find an opportunity to go all in with my full combo. Making sure to have 4 stacks from E, Go in with R -> E -> Q follow them using Q when up, followed by ignite if needed to finish them off. If the jungle isn't near or you feel confident, tower dive them and use your pool to escape safely.