Janna is one of the best support characters in the game imho. I probably won't go too specific with this guide, but hopefully it will help.

Augment the guide and comment anytime!

Runes are pretty simple.

You could change the Seals of Clarity for Seals of Force if you wanted more AP.

Another suggestion is changing the Seals of Clarity to Seals of Force and then changing the Glyphs of Force to Glyphs of Focus.

Whatever you're more comfortable with.

IF YOU ARE A FARMING SUPPORT:

> Use your tornado to hurt enemy minions then attack the caster minions to kill them quickly.
> Your tornado, towards the end of your leveling phase should be able to kill most minions and the four wraiths in the jungle.

IF YOU ARE NOT A FARMING SUPPORT:

> If you take the route of the "minimum creep kills in order to give the carry you're in a lane with more gold via minion kills", build a Philosopher's Stone and a Heart of Gold for beginning game. And do not last hit anything! lol.
> These two items should give you enough gold ((with the huge amount of assists you get)) to start up the real build you should be going for.

> Boots of Swiftness are super awesome on Janna since she has a naturally fast movement speed already. You can zoom around shield and throw birds at people safely.

> Tear of the Goddess mixed with the Morello's Evil Tome will give you plenty of mana regen plus cooldowns from the Tome.

> Rylai's Crystal Scepter will give you enough Health to run around safely. ((Besides you're fast enough to outrun anyone anyways.))

> Will of the Ancients is just fun to have, your bird and tornado's will regen you super fast if you don't want to use your ult on yourself.

> Rabadon's Deathcap was just something random I threw in there at the end for super extra AP. If you end up needing survivability build a Banshee's Veil or something nice with armor.

AFTER THE WILL OF THE ANCIENTS:

If you end up not wanting to build the "Rabadon's Deathcap".

> Build Suport-ish: Aegis of the Legion, Soul Shroud, etc...

> Build for Survivability: Banshee's Veil, Shurelya's Battlesong, Frozen Heart, etc...

Obviously everyone likes their own combination of Summoner Spells. Here is what I use and why.

I REALLY enjoy Clarity so I can stay in a lane for a long time and harass like crazy, also since you're support you can throw up clarity to any low mana'd ally.

For the obvious reasons escaping.


Other Possible Spells.

Teleport

Clairvoyance

Ghost

This bit is easy.
> Stay in the back
> Throw up shields on allies with low health
> Throw your bird in to help your carry chase, to help allies get away, or to use as a mini nuke. ((Trust me, the bird HURTS!)
> Use your ult to heal your whole team when they are all low or use it quickly to escape. It will blow all enemies away and make it easier to run away. ((You can even use it to blow enemies into your tower to get easy kills))