Hey guys!

This is my first guide, so please don't strike too hard on the visual part of this guide so forth. I will try to make it organized, but I can't promise that some of the chapters won't overlap eachother (:
As you can see, it's all about the little rolling armadillo who knows how to stamp on the ground :D
I personally have found this set to work well, and as of last evening from writing this Introduction I got a score of 14-2-16. I pretty much carried my team to the win, although I wasn't the only one doing good ^^

Greater Mark of Magic Resist helps you in the beginning to easilier take the lvl 1 spells from AP-characters in early laning.
Greater Seal of Armor is for taking regular hit as well as early hard hitting AD champions.
Greater Glyph of Scaling Magic Resist gives a good amount of magic resistance after gaining some levels, and raises untill you get to lvl 18.
Greater Quintessence of Health Gives a good amount of health for early game survival.

All of these combined gives you good early game survival, as well as a slightly improved magic resistance mid and late-game.

Not so much to say about the Masteries, except I find that taking one point in Cripple is essential for anyone looking to use Exhaust at all. Upgrading Ghost with the Haste mastery is also quite nice, as it makes it slightly faster and makes it last longer, which makes your capabilities of defending towers better. Aside from this, it's a pretty standard set of Masteries for a tank.

For Summoner Spells I have chosen Exhaust and Ghost, within good reason.
Exhaust because it provides a lot of help in teamfights, and is brilliant along side of Rammus' skills. (I will explain this in the "Gameplay" part of this guide)

Ghost is a nice spell in combination with Rammus' Powerball skill, and makes it easier to defend towers that are being attacked. Most importantly though, it makes it faster in the way that you can catch the quicker foe's, Taunt them, and kill them with the rest of your team.

Other Summoner Spells:

Teleport which makes it very easy for you to be a tank that is active all over the battlefield, and more importantly, there's the well known combo, of recalling and then teleporting right back in there afterwards, which makes you a good defender of your tower, and hopefully, after having lost all that health, you will also have damaged you enemy a bit, and can then come rolling with full hp and mana and finish them off. Aside from this, there's the combo of using Powerball before using Teleport, thus being able to roll right into the face of your enemy.

Flash is very good for both getting to an unexpecting enemy and taunting them, and can also be used to escape sticky situations. The minus about this spell, is that it is as unexpected for your teammates as it is for your enemies, so your teammates might not make it over to you to kill the target.

Heal is usefull to yourself and to your team, however maybe not as effective as the Ghost and Exhaust combo.

The reason I pick Powerball as the first skill is solely for either catching an opponent in the very beginning or for running away. The reason I don't level it up until the end after this, is that when you level it up, it costs more mana, and doesn't make itself any faster at all, and since the purpose of the skill(IMO) is only to catch people and not to damage, it serves no purpose at all to level it up until the end.

The most important skill for Rammus is Puncturing Taunt, however at the same time, it is important for Defensive Ball Curl to be at a decent level while leveling Puncturing Taunt, since, while taunting someone, need to be capable of taking the hits they will put on you, and the increased armor and magic resistance from Defensive Ball Curl is a great help for this.

Aside from these skills, obviously just level up Soaring Slam whenever it is possible.

You start off with Doran's Shield and a Health Potion, and choose your first skill, Powerball.

As soon as you hit the 850g head back to your spawn and get the Mercury's Threads. These help you with some reduced CC, which is quite important, as well as the obvious movement speed, and a decent amount of MR to start off with.

The next item, you should get, unless the entire enemy team consists of AP champions, is Thornmail, which gives a great amount of armor, also increasing your attack damage, because of Rammus' passive, Spiked Shell, and aside from this returning 30 % of recieved damage from regular attacks to the user: This is very effective versus squishy melee dps'ers.

Your next item after Thornmail should depend on who you are facing on your lane.
If you find that there's an AP champion dealing a lot of damage to you, you should go for the Banshee's Veil, which's passive is very well functioning if you find yourself being harrassed a lot. If you do however happen to be lucky enough to face two Attack Damage champions, you can go for Sunfire Aegis right after Thornmail.

After the purchase of either Banshee's Veil or Sunfire Aegis, it would be wise to invest in some Health Points. For this, the best bet, would be Warmog's Armor as it provides a nice amount of Health Points and a nice amount of Health Regeneration.

If you decided to buy Sunfire Aegis before Banshee's Veil you may however not need Warmog's Armoras much at this point, since Sunfire Aegis also gives a little HP. In this case, you may want to get your Banshee's Veil before getting Warmog's Armor depending on the nature of the game at this point.
After having gotten Mercury's Threads, Thornmail, Sunfire Aegis, Warmog's Armor and Banshee's Veil you will want to get that last insurance for your survival, which will be Guardian's Angel. Sell your Doran's Shield to get this.

Now your in as good shape when it comes to items as it is possible.

Note: Against a team with not so much Crowd Control(Slow, Stun, etc.) it may be beneficial to invest in Force of Nature instead of Banshee's Veil since it provides more general magic resistance. The best reason for getting Banshee's Veil is only it's passive protection, and mana increase.

The basics of your role in the team is basically to tank, however the only way you can tank, aside from taking incoming skills from enemies by standing in front, is to use your Puncturing Taunt and just hope to God that your teammates will follow when you go to Taunt someone.
If they do not, it may mean a death for you. Of course you need to make sure that your teammates understand that you are heading towards taunting an enemy, and using Powerball, and going a little back and forth usually makes them understand this. Then you will aim for the squishiest one you can get to, use Puncturing Taunt on them, use Defensive Ball Curl and then Soaring Slam. If your teammates are with you, the target should be dead in no time. If your teammates have been fed some, you can even kill tanks at only double the time of a squishy.

If you are succesfull in taunting the enemies you may also occassionally get kills, which will earn you more money for your build. People may call you kill stealer, however, in my opinon, which should be the opinion of anyone; The stronger the tank, the stronger the team. It is no shame to get kills as a tank. It will only be a pain to your enemies. If you are going on a kill streak, your teammates are well to invest in items like Mejai's Soulstealer, Leviathan and Sword of the Occult, since they also gain stacks from assists after all.
When I say this, I'm not saying you should aim for kills, but hunt if your teammates aren't fast enough. There is a nice combo hidden in using Soaring Slam and afterwards Powerball, which makes it easier to damage your opponent in a chase even if they have Boots of Mobility and Ghost at the same time.

In the end, all we can conclude, is that Rammus is an all out amazing tank, if not the best of the game. And this should be abused! He is aside from being a very strong champion also very very fun to play, which makes him so fantastic, that I couldn't help making him my main :D

Anyways, thanks for reading along! I hope you found this guide usefull :)
See you, for now :)