Heimerdinger is an often overlooked champion, with many stating he is in fact useless. This is utter nonsense. He is amazing in lane, a great pusher, and can throw massive amounts of damage around. This build is one of which I use for Heim. Be the surprise carry, and make all those who believe he's useless think again.

I build mostly flat AP runes, with AP over time Glyphs, this means that you can be an even more deadly force early game than normal. Heim is excellent for getting first blood, as after he gets his W, the damage he puts out is immense for low levels.

If, whilst playing Heim, his mana burning is becoming a bother, mana regen Marks or Seals can replace the AP ones, at the cost of early game power.

Not much to talk about here, just some basic survivability masteries on top of the few AP enhancing ones, with some points in mana regen as well. You can run out of mana quick as Heim, especially early game, and any mana regen can help.

The first item you should buy before heading out to lane is the Amplifying Tome. This starts off your build towards the Rylai's Crystal Scepter, and gives you even more harassing power. You can, if worried about your health, start off with a Doran's Ring, however your build will take a little while longer to complete. The Rylai's is also not just helpful for it's AP, but also for it's health boost (Heim is a rather squishy champ) and it's slowing effect, allowing you to position yourself for tower placements and more spells whilst they're slowed.

The next item is the customary Sorceror's Shoes, the magic pen excellent for cutting through champs.

The Archangels Staff is an insanely good item for all AP casters, and, if very late game you feel you want more AP, you can sell off all other items except for your boots and Rabadon's, and fill up with these, your nuking power will skyrocket.

The Void Staff is a maybe item, useful only if the enemy team begins stacking more magic resist. It can easily be replaced by the Abyssal Scepter, if you're the one needing magic resist, or another Archangels, purely for more AP boost.

Zhonyas Hourglass is a special item, and won't always come in handy for Heim. The AP is great, and the armor increases his survivability immensely, however the active isn't ideal for Heim, he should never be in a position where he'd need it unless he knows he can finish off all the enemies around him.

Getting a point in the H-28G EVOLUTION TURRET will help laning immensely, and help farming even more. But your main harass and damage output comes from the HEXTECH MICRO ROCKETS, powerful and guaranteed to hit, as long as you're in the right position. His range is fantastic for this, and it can be cast whilst fleeing, maxing this first gives you a lot of power early.

Getting the H-28G EVOLUTION TURRET to level 3 early is good as well, as then you are able to place two turrets, further increasing your farm and helping out allies.

Your ult, UPGRADE!!! doesn't come in handy very early game, it CAN be used to get a kill early, but it's far more useful during teamfights. Your level 3 Q is more important than this, and should be acquired first.

The CH-1 CONCUSSION GRENADE is amazing, a stun and mass damage, but it's very unreliable and hard to hit. This is the last skill you should max, even though it can come in very handy at all times, but it's slow speed makes it less useful than your other skills early.

I personally use teleport and clarity, so I can jump straight back into battle, and clarity to avoid Heim's notorious mana guzzling. But, ghost and flash are equally useful, as Heim doesn't fair well when caught by enemies.

PROS:

Insane laning potential
Good farmer
Crazy damage early game
Underestimated

CONS:

Squishy when not built correctly
Can be outscaled late game by other AP carries

Heim is an amazing champ to play, if you can play him, and if you can't, then he can end up just being a feed. He can farm well, and thus can outlevel most champions, and can push insanely hard in any lane, but it must be noted that other AP carries can outscale him and put out more damage late game.

Heim can be used as a partial jungler, but pure jungling from the beginning of the game is not advisable. His turrets take the aggro while you do the damage, and that can be especially useful for picking up buffs or a surprise first Dragon capture.

Use his turrets to defend allied lanes, scout bushes, and get a surprise attack in. Heim CAN be effective all by his lonesome, and is great at taking mid by himself, but later game working with your teammates in order to keep yourself alive and dealing damage is a must. You can throw your W and E out from behind your allies, due to their range, and can initiate a teamfight through baiting into your turrets and unleashing all your abilities.

Also, his passive allows you to help allies heal faster, and that bit of healing can be the difference between life and death.

Heim has the distinction of being the only champion who can heal allied towers. If your tower is hurt, consider standing by it to heal it up a bit, whilst it would take a long time to fully heal a tower after a barrage of attacks, the healing you do means that the damage done must be redone, keeping your lane alive for longer. This is especially useful when being pushed back to your Nexus towers, as when defending you'll be standing by them and healing them, but take note that your heal is very slight, and cannot outdo even a minion wave attacking.

His W and E skills can be used through walls, and thus can get surprise harass or kills in.

The turrets you put down can be placed in brush for a little surprise, or placed to keep a minion wave from pushing to your tower while out ganking.

A very important part of playing Heimerdinger is to FARM, when your turrets get minion kills, they count for you, so place them often and everywhere you can, to get as much CS as you can and to level as fast as possible.

And there you have it, Heimerdinger, the Revered Inventor, is a very viable option when it comes to AP carries. With his unique style of play, he can harass enemy champs, push a lane, and get CS from the other side of the map. As long as you use him right, his nuking power is quite great, and this build allows him to follow for another round of nuking without as much danger of dying.