Hi this is my first guide so please give me suggestions and tips appreciate it. I'm pretty new to league with about 6 months of experience. When i started league i used Mobafire as a source to learn more about champions. I'm currently around 1500 solo queue elo so i'm not too experienced. I learned nunu when i first started rank finding out i can't get the role i always want. I found him to be a strong support with great pokes /buffs / and an awesome ultimate

Before we go any further I would like to explain the good things about nunu and the flaws.

Pros

Consume can save your life if your ignited after a battle
Good pokes if facing another support that has no shield/heal
NUNU BOT BEST SKIN/LAUGH EVAR!!!!
Can help protect adc or ap since he has slow and bb.
Bloodboil has a 15 second cooldown and last's 15 seconds almost like giving an adc 65% attack speed and 15%% movement speed once mastered.
Good timing on ult can help get as much out of it as possible.(Like waiting for the fight to start and waiting for most ccs to be used.)

Cons

Ultimate can he stopped by silence,stun, etc and can be avoided by using flash or something like ezreal's .
Can be targetted by people when your ult is on (even though it should help the team like letting the ad auto for free)
No stun only slows for ganks.

During Lane phase Nunu's require ment is to ward tri or river so the adc can farm freely with vision on maps when the enemy jungler is ganking. Nunu should also keep a constant on the adc. Around lvl 6 it's best to keep a ward/vision on dragon to have vision on a dragon that can give a big advantage for the team that kills it.

If you find the time with your lane pushed and dragons safe for awhile feel free to help the adc take Red buff,golems, and wraiths. Nunu's even at level 1 can be helpful as you consume the monsters early and bloodboil the adc and maybe ice blast if you have alot of mana.
However lets not forget nunu's passive It can help you sustain your mana in the jungle and maybe during fights as 5 each basic attack gives u a free spell. It's not the best passive for a support in the beginning since its best the support doesn't auto the minions as it can push the wave. But it's still useful and can save alot of mana.


If facing a support like it's best not to spam unless you know it can do some dmg with slow and the ad's pokes. Since taric has a heal it would just counter nunu's dmg for . It's best to wait for taric's stun to be in cd before ulting since it is his only cc to stop nunu's ultimate.

If facing a champ a Janna who has it can competely waste nunu's pokes along with giving their adc some dmg to harass. Janna can be a tough support to lane agaisnt with shields/slows/knocking people with q and an ultimate that heals and can cancel nunu's ultimate.

During Mid game dragon should be gone and a few turrets also, and some team fights could occur defending turrets/fighting for dragon/ or counter jungling as a team hoping to pick someone off. It's best to time the dragon as it respawns every 6 minutes. If you time it correctly your team can get the dragon fast giving your team 190 gold each.
You should also remember to ward where you can but the basics are here:

I took this picture from jhoijhoi hoping i can explain the basic's of warding during mid/late game.

IF your team is willing to fight together for a buff like blue/red from their's buffs respawn after every 5 minutes.

And lastly a good nunu is best not engaging but protecting the adc/mid because nunu keeping a CONSTANT bloodboil on the adc can give you guys a huge advantage and maybe win the fight. Try to time your ultimate properly after most cc's are gone attempting to take most effect of absolute zero.

Skill sequence is like any other champions with the ultimate at 6/11/16.
Its best to pick at 3 and max it last as it does heal you but the skills and be put more effectively on other skills 1st.
Now I usually max 1st to increase our poking ability. However it could change as :
EX: has heal which can easily heal up nunu's pokes along with some armor for 3 seconds.
If I face a champion like soraka I pick up Ice blast at 2 and max 1st to boost the adc's power early.
Now for Bloodboil i max it 2nd if facing a champion without much heal or no heal at all.