A H-28G Evolution Turret can act as a ward, though this is not recommended since they cannot stealth, and auto acquire enemies thereby revealing them, and offline turrets only give the sight range equivalent to that of a Noxious Trap.
Use them as such only if you find yourself repeatedly ganked.
Good H-28G Evolution Turret placement is crucial to their effectiveness. For example, placing one at the back end of your minion wave would make the turrets near useless (as the enemy minions are far away from the turret).
Heimerdinger is capable of stagnating the mid lane and taking a turret without ever becoming aggressive. Coordinate with your jungler and attempt to ward all possible paths to mid so that you can be aware of ganks, then handle laning phase by maxing H-28G Evolution Turret and focusing on maintaining a 3-turret spread that will "catch" and vaporize every minion wave and cause your minions to shove to the enemy turret. This does 3 very important things. Firstly, it shrinks the lane down to less than half of its normal length. As a result, the enemy will have to CS under their turret for almost the entire game and you will have some soft gank protection. Second, the turret formation (and maxed turret level) makes it too hard for the enemy to simply wipe away the turrets. They will focus spells and damage on taking one down, and you can instantly rebuild and punish them with a burst combo. Third, the constant lane shoving will inevitably cause your minions to chip away at the enemy mid turret. It is possible to bring an enemy mid turret down without ever forcing your opponent out of lane or using basic attacks against the turret.
H-28G Evolution Turret, when set up before minions appear, can be used to disrupt the enemy jungler, forcing an earlier recall, and giving info on where the enemy jungler has been.
Keeping turrets clustered is good against non-AoE based champions. Keeping them away from the minion path cuts down the AoE's effectiveness even more. A tight cluster can block skillshots such as Dark Binding or Mystic Shot, but are susceptible to AoE spells such as Tormented Soil.
Hextech Micro-Rockets is an extremely powerful tool for harassment and zoning, due to its long range and high concentrated damage, functioning as Heimerdinger's main source of damage early game.
Hextech Micro-Rockets will hit the first enemy it makes contact with, so try to catch your opponent in an open area before using it for maximum effectiveness.
CH-1 Concussion Grenade stun is difficult to land by itself; throwing it after allied disables have been placed guarantees success. Being closer to the target area is also helpful as it lessens the travel time.
H-28Q Apex Turret summons a greatly enhanced H-28G Evolution Turret that deals splash damage, charges its beam attack faster, and slows its attack targets. It's best used as a defensive tool when an enemy directly attacks Heimerdinger, or during a teamfight in which you don't need hard crowd control or burst damage, as it deals high sustained damage that makes fighting near it very dangerous for your enemies.
One of Heimerdinger most effective tactics is to quickly set up as many H-28G Evolution Turrets as possible and an H-28Q Apex Turret and bait an enemy into fighting you while keeping yourself safe with the Zhonya's Hourglass active. This tactic is most effective by mid or late game where enemies are more likely to over commit to a fight and by this time, your turrets will be putting out a lot of DPS.
CH-1 Concussion Grenade can be used to reveal a large area. This combined with its long range make it excel at scouting brush or jungle areas.
Leaving a lane to buy items can be more beneficial to your lane if you have the summoner spell Teleport. By placing your turrets in a bush out of sight and recalling within the sight of your enemies then buying items and using Teleport back to the hidden turret can cause your lane enemies to over extend trying to kill your partner when you come out of the bush and kill them.
Before leaving a lane, place both turrets and then Teleport back to one of your turrets being attacked since it will be invulnerable during the teleport time.
If Heimerdinger throws a CH-1 Concussion Grenade into a bush, he gains vision of it regardless of whether it hits something or not. It isn't recommended to stay in the bush if he spots you in this manner.
Heimerdinger is an incredibly squishy champion if caught out. Take any and all opportunities to attack him if he separates from his turrets or attempts to roam.
Additionally, Heimerdinger is weak in team fights if he has no chance to set up turrets. If a team fight begins and he is without his weaponry, have your team stick on him and melt him as quickly as possible.
If he is allowed to, a Heimerdinger with his turrets set up and UPGRADE!!! ready can be difficult to penetrate, as a fed Heimerdinger who is able to set up turrets is one of the most powerful opponents in the game.
If all your abilities are on cooldown, don't chase him around his turrets, as the turret damage will quickly add up.
Unlike most mages, Heimerdinger can bring down fighters alone by kiting them around his turrets and landing a good CH-1 Concussion Grenade.
Try not to push Heimerdinger to his turret, as his passive allow him to hold it for an extremely long period of time while farming easily.
His turrets will also be hard to take down when near a (real) turret.
Veigar can be considered a good counter to Heimerdinger when they meet in a 1v1 lane. Veigar can gain AP from Heimerdinger's turrets by farming his Q, both of them have similar mobility, Veigar can land his stun more easily, his W can one-shot H-28G Evolution Turrets in the mid game, and Veigar, in the early game, isn't a pusher. Also, Veigar's ultimate can finish off Heimerdinger before he can use his UPGRADE!!! if he can land his combo in time.