My first real guide. As pointed out in other guides, support is really important in the meta, and often underrated by players. With Nunu, you'll need to have a ranged carry (I think). Also, lane match-ups are very important. If anyone can interrupt your ult, you'll be in trouble. Examples would be Blitzcrank (punch, or grab), Taric (stun), Tristana (her ult pushes you), and many more. Aggressive long range champs can also cause problems for Nunu, especially in this build, as you'll have less healing available to you at the start.

As you should know, as a support your job is not to kill minions. Your job is to help your carry get fed. Killing enemy champions helps, but be careful while doing so. Don't push the lane unless you are sure you won't get ganked. Try to harass enough to disrupt their carry's farming. Keep your carry killing minions, that's their job for the first half of the game.

You will not get kills with this build. You will not get wins with this build.

I repeat: this build will not get you a win.

You will get wins by taking care of your carry, disrupting their carry, building map awareness for your entire team, and essentially babysitting EVERYONE, not just your lane partner. Warn anyone of a possible gank. Be supportive and helpful. If you have a relatively passive lane, since your not busy with farming, you can look at the minimap about 75%% of the time. I know it's only 10% of your screen, but it's easily the most important. Be the one who keeps track of the dragon timer. Supports may not always get credit for the win (the carry you babysit might), but they are the ones that can most easily prevent a loss. It is a challenging position, but one that can be very fun.

At the beginning your focus is gold (without CS) and possibly helping your AD carry score a kill (by using Blood Boil and Ice Blast). Try to utilize Visionary by attacking minions, but make sure you don't steal gold from your carry, or end up in a bad position. Using Consume on a siege minion when it's at full health will allow you to heal, and still give the gold to your carry.

You have Heal and your health pot for some early healing, which allows you to hopefully delay consume for a while. This is also why we build as much as we can in defense.

Always keep an eye on the minimap. Know where your jungler is. Know where their jungler is (much harder). Ganks don't work nearly as often if you give your team a heads up.

Mid begins when you have your gp/10s and keep wards up near dragon and some jungle points. Make sure your carry gets fed, but with your ult, ganking mid after warding the river is a possibility. You can also help your jungler take down dragon, but make sure the enemy doesn't have sight on you: use a Vision Ward, it could save you and your jungler.

Eleisa's Miracle: grab it at 14 or 15, or not at all. You want to keep philosopher's stone as long as possible. By reducing your heal cooldown, it makes heal almost useful again late game. Don't take if you don't have heal.

Shurelya's Battlesong is your alternate build path for philosopher's stone. Remember to use the active when running, it's pretty much Ghost, on steroids, with a shorter cooldown (54s with our masteries). A very good choice.

Runic Bulwark adds some more MR to Aegis of the Legion. A little expensive, but nice if your team is getting beaten down by magic damage.

Shard of True Ice is a sweet upgrade to kage's lucky pick. You keep the gp/10, get more AP, help your team with it's mana regen, and get a pretty sweet active for less than 1000gp. Almost never a bad choice, and can really help your team in certain situations.

zeke's herald is nice for your AD carry, and will probably help your whole team at least a little bit. It's slightly expensive for a support, so don't count on getting it.

Oracle's Elixir lets you destroy the enemy. DESTROY. Crush their wards, and make them lose map awareness. Then destroy them. Alternately, Vision Ward works great for this, and helps spot pesky stealth champs, when they're trying to sneak around. Then destroy them.

It may feel odd to not take 21 in a tree, but as a support, you need Greed in utility. You want Meditation because if you're harassing early game (which you should be) you will run into mana problems. Visionary is tricky to utilize, but if you can, you should have no problem.

Taking things in the defense tree is meant to make you less squishy late game. The main point is to get health, armor and magic resist. You also have 1 or 2 points that you can move around between: Summoner's Resolve (useless if you don't take heal), Perseverance, Relentless , and Tenacious . Pick based on your play style.

Flash is pretty much required for anyone these days. It's simply too good of an escape or an initiator to pass up. Mastermind and Summoner's Insight help fill up your support tree, and make the cool down on this bearable.

Heal is what I recommend, it's useful early game to help your carry, and helps compensate for not taking Consume often. with Summoner's Resolve it also gives you 90 hp in the end, which isn't a bad thing.

Exhaust is possibly viable alternative to heal. It's popular for supports, and can either help a kill, or if running away from a 1v1 (because honestly, fighting is not your thing), it can further slow the enemy down. But remember, you have Ice Blast which past level 3 is better at slowing the enemy, and has a way shorter cooldown.

Ignite might be a good idea if your carry doesn't have it and you want first blood. That money certainly helps you early game. With a shorter cooldown via Mastermind , you can use it often enough that it might be useful. Getting a kill closer to mid game could give you the advantage to get dragon as well, really beginning to tip the game in your favor.

Teleport is usually not the worst choice. It's a bit situational, and so often isn't the best choice either. If the enemy gets a quick kill on you, or if you just need to buy more wards, it allows you to get back quickly. It can (of course) launch an almost guaranteed kill top if coordinated with your jungler. I personally like it, but it's not really a spell for the support role (traditionally).

Runes might not be my strong suit, just a warning.

AP at the beginning from the glyphs makes your harass with Ice Blast a little more scary. Also helps you heal with consume a little.

With quints and seals, we get +5 gp/10, which is a lot compared to the 16 gp/10 base. It helps rush philosopher's stone and kage's lucky pick, which will bring our passive gold gain to an even 30 gp/10 (180/minute), which is 2 sight wards a minute, plus some extra to save for "real" items.
With Ruby Sightstone, altogether you could have 10 wards around the map, if all you did was ward. (NOTE: I do NOT recommend doing this. It's just neat to see.)

For marks I took magic penetration. Doesn't do a whole lot for you, but does boost your Ice Blast and Absolute Zero, possibly meaning an extra kill in late game.