Simple season 6 guide to Lulu mid.
I have made this guide to show Lulu's strengths and how to use her effectively.

Lulu brings a lot to Summoners rift and to your team. She is known for her utility and extremely safe laning phase as well as strong late game scaling. Her entire kit revolves around harassing your opponent while keeping yourself and your teammates safe. Using Lulu high utility in the most effective way will greatly increase your chances of winning.

Pros

Wave clear
Very good at avoiding ganks
High poke in lane
Can win most auto attack trades because of Pix, Faerie Companion
Utility that scales well into the late game
Squid Hat

Cons

Squishy
No way to lock someone down (immobilize) pre 6
Very high mana costs
No sustain
Not the highest damage late game

Lulu is very flexible in the way you can play her. Whether it be aggressive of defensive. You can use your Q to farm and harass your opponent down. You can also use your E to extend to range of Q for more tricky play. Use E to block incoming damage. Save W for when your being ganked or receiving a gank to get the kill or run away. W also should be used to prevent the other mid laner from wanting to get aggressive on you by stoping all their damage and hitting them.

Q- Glitterlance

Cost: 60/65/70/75/80 Mana
Range: 925
Pix and Lulu each fire a bolt of magical energy that heavily slows all enemies it hits. an enemy can only be damaged by one bolt.
Lulu and Pix each fire a piercing bolt dealing 80/125/170/215/260 (+50% Ability Power) magic damage, slowing enemies hit by 80% for 1/1.25/1.5/1.75/2 second(s). This slow decays over time.An enemy can only be damaged by one bolt.

W-Whimsy

Cost: 65 Mana
Range: 650
If cast on an ally, grants them Movement Speed for a short time. If cast on an enemy, turns them into an adorable critter that can't attack or cast spells.
On Ally Cast: Target ally gains 30 (+10% Ability Power)% Movement Speed for 3/3.5/4/4.5/5 seconds.
On Enemy Cast: Polymorphs an enemy champion for 1.25/1.5/1.75/2/2.25 seconds, disabling their ability to attack or cast spells and reducing their base Movement Speed by 60.

E- Help, Pix!

Cost: 60/70/80/90/100 Mana
Range: 650
If cast on an ally, commands Pix to jump to an ally and shield them. He then follows them and aids their attacks. If cast on an enemy, commands Pix to jump to an enemy and damage them. He then follows them and grants you vision of that enemy.
On Ally Cast: Commands Pix to jump to an ally and then follow and aid their attacks instead of Lulu's for 6 seconds. If the ally is a champion, Pix shields them from 80/120/160/200/240 (+60% Ability Power) damage for 6 seconds.
On Enemy Cast: Pix deals 80/110/140/170/200 (+40% Ability Power) magic damage to target enemy unit. Pix then follows and grants vision of them for 4 seconds.

R-Wild Growth

Cost: 100 Mana
Range: 900
Lulu enlarges an ally, knocking nearby enemies into the air and granting the ally a large amount of bonus health. For the next few seconds, that ally gains an aura that slows nearby enemies.
Lulu enlarges her ally, knocking nearby enemies into the air. For 7 seconds, her ally gains 300/450/600 (+50% Ability Power) bonus health and slows nearby enemies by 30/45/60%.

Ignite

Good if you want that extra little push to get a kill.

Barrier

Good if you need a little more protection

Exhaust

Good if you wanna guarentee you don't get all in. Also good if the enemy team has lots of damage threats.

Flash

Best summoner must take

Teleport

Good if your afraid of using too much mana or being poked out of lane. Also good for map control

Runes

Standard AP Mid lane runes

Masteries

12/18/0 masteries. The reason for this is because Thunderlord's Decree is really strong on mid laners right now. Also very easy to use with Lulu with a few abilities and autos. The reason for Thunderlord's Decree and not Deathfire touch is because Thunderlord's Decree does more damage in shorter bursts instead of constant poke. Then 12 points into the Ferocity tree because it does more damage then the Resolve tree would be. Take the 12 Point in resolve tree if you want that safety but remember your trading away your damage for it.

Pre 6

Lulu can be played very aggressive early with her strong pushing speed. Your gonna wanna harass with your auto's they do more than you would think. Remember you can use your E to extend the range of your Q to poke people out of lane. Be careful of your manna supply

Post 6

Once you hit 6 your very hard to be kicked out of lane because of your ult. Continue to play the lane accordingly only now you have better all in potential and skirmishing power.

Roaming

Don't be afraid to roam as Lulu her roam power is very underrated. Lulu can get around the map very fast with the help of her W. Her Q slow is often all you need if a lane is overextended to run someone down and pick up a kill.

Lulu Brings high utility to team fights. Mainly Lulu is meant to buff up other member of your team (adc). Im gonna go over every ability and how they can be used.

Q- Glitterlance

This can be used to slow to catch up to fleeing targets.
Good slow for kiting/peeling or running away
Good source of damage

W-Whimsy

Speeds up your team members so they can catch out targets that out of position
Makes you or 1 of your allies very fast so they can get away or
Defensively it can be used on an enemy champion to prevent them from doing damage (Recommend on whoever does the most damage or is the most threatening)

E- Help, Pix!

Can be used to shield allies (Best choice usually)
Used on an enemy champion does a bit of damage and grants vision of that champ.
Move Pix around which allows you to extend the range or angle of your Q

R-Wild Growth

Used to save allies by giving them a bunch of Hp and making them huge also slowing people.
Also is a nice AOE knock-up