Starting E you should step up if the enemy allows you to start auto attacking the melee minions before they meet in the middle, identify witch one your minions are attacking and avoid attacking it. When it gets low, cast E on it and last hit, begin focusing the one with E, if you set it up right you should get all 6 minions and almost all the mana spent back along with keeping your casters.

try and make the enemy miss as much CS as possible early game to set them back and weaken them. while the wave is under tower you should never be any further than between the two walls of the river or else you risk being ganked.
look for early backs to keep pressure on the enemy and keep an item advantage early by pushing and backing, using teleport to get back quick if you need to.

a trick to use is that towers wont change targets among minions and your voidlings, if an enemy backs and you want to siege his tower with voidlings, wait for the tower to target a full health melee minion or a cannon minion before summoning them, the voidlings gets more damage off than you'd think

when farming with E it may jump to the enemy champion, dont try to hit Q right away, let it sit for about a second then cast it just behind them so if they stay still or move back they get hit. resetting your E deals lots of damage, at level 2 with both abilities at rank 1 and E has ticked for 2 seconds a reset will deal a total of 190+185%AP magic damage, not including Summon Aery, scorch and cheap shot damage.

it is here you should try a little more to set up for ganks, if your jungler can deal ok damage you can bait an all in and R them for a free kill.
if you've already killed you lane opponent and still have your R you should look to roam with teleport or group for dragon or herald, with your R you can stop any attempts to steal by the enemy jungler. its important for you to get your Ultimate hunter stacked up so that you can use your R whenever you need it.

If you cant roam for any reason, push for first tower, mid is a great lane to have opened up for a big push later. for second tier tower you need your team so really group up to get shut downs and objectives with your team.

Late game you need to stick with your team, only split long enough to push the wave, reason being you can take the strongest enemy and suppress them as well as spread damage with your other abilities to weaken enemies but your R late game is up every 30 seconds and so dont be afraid to use it right away if say the 20/2/16 Vayne pops up in your back line.

By now some enemies will have purchased a QSS or a Mercurial scimitar, take note of who and simply dont R them until you see it go down, this eliminates a good bit of value they get out of it, especially for QSS.
make sure to keep wards up so your team has vision of the enemy.