This is my first guide and I start with my main champ Janna. She's one of the best (in my opinion the best) Supporter in LoL and not just your AD Carry can escape quickly and farm well, your ability to survive is enormous.
English is my second language so please correct me if my grammar or vocabulary is wrong ;).

This is the biggest job of a Supporter: PLACE WARDS !!!!
You have to ward at least Baron and Dragon and it's better you ward Blue and Red, too. Buy ALWAYS wards (that's the reason why support is full equip with 5 items) and don't care if you need only 200 gold for next item, wards are more important. And don't wait at spawn for more than 40 gold, your team needs you. It's very easy to place wards with Janna, thanks to her movement speed.

So please, buy wards it can save your whole team's life.

Why not?
Well, your Eye of the Storm scales with 0.9 AP, your Howling Gale with 0.75 AP and your Zephyr with 0.8 AP, but your Monsoon only with 0.35 AP.
And the most important thing: you don't have to deal TONS OF DAMAGE and you have to get as many auras as possible. You don't need a big shield to save your team mate's live, more important are armor, magic resist and attack damage/ ability power auras to maximize their potential to survive and kill.

Pros:

Very good shield
Knock up
Slow
Good AoE heal
Knock back
Insane map mobility
Can keep up with the AD Carry

Cons:

Squishy early game
Mana intensive
No heal pre-six

Take Clairvoyance to see the enemy equipment at the beginning of the game and spam it to TOP and MID to prevent Junglegangs.
Clairvoyance is my favourite summonerspell because you can see EVERYTHING on the whole map. I would take it as an AD Carry if I wouldn't need Exhaust or Ignite.



Take Flash to jump over walls to escape.




You can also use:



No comment. You know what it is. I don't like it because it reduces the healing effects.





If you have mana problems or you have a mana intensive champ, take it, but it's better if you don't waste mana and take mana manipulator.

For Runes the best choice is:

Greater Quintessence of Avarice:

This is a very good Rune for Support because if you get the mastery gold you'll get DOUBLE gold without items !

Greater Glyph of Clarity:

This is very important on Janna. Try to waste NO MANA and give your AD Carry only the shield if he's getting attacked or if he's going to attack.

Greater Seal of Resilience:

Same here. You'll only play against AD Carries.

Greater Mark of Resilience:

You will be the one who supports AD Carry, so you'll play against AD Carries. If you like Magic Resist for them, get them.

Janna's Q-ability is Howling Gale

and it's a long range knock-up-skill shot which is getting stronger over time. To support don't hold it and just fire it because you don't have to kill them you just have to disable them. If you want to escape or save your Carry, do the same.


The W-ability is Zephyr

and it has an active and a passive part: the active slows a single enemy and the passive gives you permanent movement speed and allows you to move trough units.
Try to slow the enemy while attacking or running away, so your AD Carry can escape or kill.


Your E-ability is Eye of the Storm

it's your OP shield giving your AD Carry 50 bonus attack damage and is almost always ready. It's your main support ability and your main ability as AD Janna (It works great !). Just give it to your lane partner if he attacks or being attacked because it's VERY MANA INTENSIVE.


Your R-ability is Monsoon

and your ulti is epic !!! It's a knock back longterm AoE heal. You can use it to get distance between the enemy team and yours or to heal. I mostly use it for the push back and in team fights for AoE heal.

Ionian Boots:

You're fast enough (451) and you need cooldown so you can cast your shield nonstop on your AD Carry.


Aegis of the Legion:

This is your first Support-Item and it's cheap :D It gives you allaround protection and an Aura with attack damage, armor and magic resist and for you: Health !


Your next item is Soul Shroud:

It gives you tankiness and a very good aura !
Get the whole thing after you get Kindglegem at once.




The next item is Shurelya's Reverie

It gives you very good mana regen, health regen, health, and most important cooldown.
It's the most important item for a lost teamfight and quick escape.


Your last item is in my opinion Stark's Fervor.

Your AD Carry gets 20% bonus life steal, 20% bonus attack speed AND an armor reducement.
Take this if you have more AD in your team.

If you have more AP in your team, take Will of the Ancients.

DON'T TAKE THEM BOTH, YOU ALWAYS NEED A FREE ITEM SLOT FOR WARDS !!!!!

Replace

with

if you get CC'd a lot.


Replace

with

for the most INSANE map mobility !

Replace your starter items with

if they have no jungler and if you have a mana intensive lane partner, but I wouldn't recommened it.


Replace

with

if you are a AP team or you need an extra boost for your ability power with an included aura.


Replace

with

if you play against a heavy AD team and they're raping your *** and you need an AoE slow.


Replace

with

if you play against a heavy AP team and you're instant death.

I repeat that this is my first guide and I hope that it's a good one :)
I published it on 16th January 2012 and included the next day Summoner Spells, Skills and new Situational Items :).