This is my first guide, and i hope it works out well.
My guide is focused around utilizing the power of Skarners passive and his Q's incentive to use it repeatedly. Picking up most of the on hit affect weapons along the way makes this Skarner build freaking scary in end game.

Pros
-Slow
-Shield
-Spamability
-One of the most muliti-purposed and most hilarious ults in the game.

Cons
-Mana hungry (Get blue buff)
-Super slow start
-fairly week very early game

I pick up basic health AD armor pen runes to make Skarner a giant scorpion wrecking ball.

using a basic 8/22/0 gives a lot of needed sustainability that most other Skarner builds get that this build lacks because i find that picking up more DPS type items makes Skarner a bigger force in end game, while getting the 8 points in offensive gives that needed boost to DPS.

Flash and Exhaust are my go to summoner spells for any melee DPS because the uses for flash are endless and exhaust is the best spell ever for chasing and running.

Clarity is viable for the early game mana hungryness of skarner but later Flash and Exhaust are better.

Ghost is also good for running and chasing

Teleport is viable but i find using W to get back to lane is fine

I get Q first than W and get E at level 4. I max my Q because its my main spell than W because the AtK speed and Movement is non replaceable.

I Build Skarner AD DPS because even though most of his abilities scale off of AD the mega pwn of his Q makes stacking AD viable. And with AtK Speed and Skarner's passive he can basically spam his Q and slow and rape and lol at their despair.

In general keeping your boots around seems to be a given but when i build Skarner, i grab enough extra movement from Lich Bane and Phantom Dancer, and Skarner's W, that you don't need boots and can get that extra Black Cleaver so you can kill stuff hardcore.

In general my items are based around the basis of getting on hit effects because of Skarners ability to stack AtK speed and kill everything.

When playing Skarner i find it better to lane with a partner who can slow or heal. When you head into a fight pop your Shield for that extra movement, throw your E at them and than spam your Q until their dead. Make sure to use your E when its up for the heal and pop your W to gain AtK Speed and movement speed.

Once i hit level 6 as Skarner i start looking for a gank. When one is set up i pop my W run in, hit them once with my Q and than ult them towards the my tower. When the ult breaks hit Q again to slow and than roflstomp their face into the ground.