Hello everyone to my Heimerdinger guide.
I wont say that im a complete pro at this champion, i played roughly around 300 games as him, but i just want this guide to exist. I will change and add some new details and information every so often.

Who is heimerdinger?
A defensive style mage, that excels at poking and pushing his enemies away. And if they are brave enough - killing them with an ease.Why heimerdinger?
He is heavily underrated,
He can go for a lvl 1 camp if he pleases,
He counters almost every single melee character,
His burst is outrageous,
He is fun and rather easy to play (but hard to master).

PROS:
+ Very underestimated
+ Decent burst potential
+ Hard to lane against
+ He is able to 2v1 (if needed)
+ He is able to take a lvl 1 camp or even a buff (if needed)
+ Fun to play but hard to master :^)
CONS:
- Squishy
- No escape and rather slow
- Useless in lane without turrets. (that's why you need to protect them)
- Kinda weak against long range carries, like Caitlyn. (she simply destroys your turrets from a far)
- Useless in teamfights if not played properly

H-28G Evolution Turret

This your bread and butter. I dont think i need to say that much. Turrets are your main source of damage. Most of the time you have to let an enemy poke you rather than your turrets, that's because they do all the work for you. They damage minions, they poke your lane opponent, they prevent enemy jungler from a proper gank. Oh if someone brave enough comes to gank you, well, he just gave you a free kill. It' almost guaranteed for you to take out one of them. And possible to take out both.

Hextech Micro-Rockets

Your second source of damage, mostly used in lane as a source of poke or combining with UPGRADE!!! for tons of damage.

CH-1 ELECTRON STORM GRENADE + UPGRADE!!! + Hextech Micro-Rockets

CH-1 ELECTRON STORM GRENADE

Well, an aoe slow + stun, what more could you ask for?!
It plays a big role in the "oneshot combo"

CH-1 ELECTRON STORM GRENADE + UPGRADE!!! + Hextech Micro-Rockets

It's a possibility to max it, manacost wont grow at higher ranks, but the damage is not as big as from Hextech Micro-Rockets

UPGRADE!!!

Well, 3 ultimates in one. Either a GIANT TURRET that deals tons of damage, or a BIG WAVE OF ROCKETS, or a ******** NUCLEAR BOMB that stuns in an aoe (like a Crescendo)

So, the gameplan:
You push your lane, this gives you a lot of possibilites:
Like taking dragon, baron, teamfighting, counterjungling, invading and setting up traps.
So, you wonder, what kind of trap you can do as Heimer?
Im talking about a thing, that some people call death wish.
(OFFTOPIC)
Screenshot is old, but still, you get an idea.
Take a bush which enemies are likely to go through, place 3 turrets, as soon as enemy comes to facecheck, you use this simple and well known combo: CH-1 ELECTRON STORM GRENADE him + UPGRADE!!! + Hextech Micro-Rockets
Most of the time, going for objectives will be your next priority, after winning a lane or losing it. In a first case, congratulations, you have won against some wanky Xerath ,
Go ahead, and help your jungler to take the dragon or rift herald or even baron nashor.
You may do so, even without taking an enemies turret previously (as an example of a strong reason to leave the lane), but also, after just a regualar push.
Push your opponent under the tower, and run up to dragon pit (for example) place a few turrets (or R+Q) to help him out with taking it faster and safer.
Then go back to your lane, knowing that you just did a great thing to your team, without loosing too much (GOD BLESS MURICA).

This subject is worth of it's own chapter.
Because no one realy ever expects that kind of burst from Heimerdinger. It always comes as a surprise.
So yeah, here are some basics:
Because in this particular guide we took barrier, we should always be aware of our potential damage.
So for instance: 8 minute, you got Morellonomicon, you can kill some random bruiser like Irelia with roughly around 50% hp.
(that's +/- magic resist)
But with Luden's Tempest you can kill this particular target with around 60% hp.
The difference is small, for some people, but it matters.
(But i usually go with a rylai's as a first item because it gives you this sweet slow, that is applied even with a regular auto-attack of your turret and some decent hp)
But it mostly comes from your personal experience.

NEVER, NEVER BE AT THE FRONTLINE.
Even if you are extremely fed, not only that you are still, an ap caster, but you are not that strong without your turrets.
And being at the frontline - means a constant position changing, that's not a good environment for Heimer.
Stay behind your team, try not to get flanked from a side, by some random Jax , try to make a safe environment for you either before a teamfight at some constant location (dragon or nashor pit, tower pushing) or after engagement.
If there is a gap-closer at their team, do your best at making him to waste his gap-close on somebody else.
If you see, that someone like Warwick is already running at you, and there is nothing you can do, just do a quick R+Q, maybe rapid tap Zhonya's.