To say in advance, this is my first build and the build I use whenever I play Rammus. I find it to be a very effective build for my play style and I hope it works for all of you as well.

*Note no Jungling tips here. This is not a jungle Rammus guide.*

I turned off requiring a comment to vote. It doesn't help anyway I realize when people just comment. "-1"

Changes: Added tooltips as of late, will be touching up some spots here and there regarding the mana regeneration changes, health runes/masteries, and Doran's shield once I figure out what I like or find useful now.

Also go check out Bguggs's Guide out as well. There's more than enough information on Rammus there on his playstyle/tips & tricks to help out anyone new to this character. It's very well written, I just don't like most of his item builds. :D ((

Ghost seems ideal to me because as Rammus, I find myself often having to chase one or more players down for my team, allowing Ghost to act as sort of a second powerball or enhancing an active powerball move.

Flash is particularly useful as well because it allows Rammus to get in the right position much easier than it would be to just path there normally. For a few examples, I use flash to skip over minions protecting an enemy from being powerballed, to jump to a target I need to taunt that second (Usually to break the cast time of an ability or save an ally), or to flash away from battle and powerball home when my health is looking terribly low.

The rune set up for Rammus is something I look at to be very adaptable with this build so basically choose what you want to use, it will not make or break this build. As for me though, I like to use:

~ Greater Quintessence of Fortitude
~ Greater Glyph of Focus for faster taunts and chases
~ Greater Mark of Insight Marks to enhance all of Rammus's damaging abilities.
~And Greater Seal of Resilience to build up more of an early game defense because I focus for regeneration items first.

Greater Glyph of Warding are a good replacement as well along with Greater Seal of Vitality I find.

If you, like many other players, hate the Philosopher's Stone then good news, I have an alternative for you now! Greater Seal of Clarity will cover all your mana needs mid to late game. ((I'd also recommend grabbing a Doran's Shield too as your starting item if you do this..))

This set up for your Masteries quite compliments my Ghost and Flash set up because of the two points into their select upgrades. This build overall though focuses on three primary details.

Veteran scars -- +48 health
Hardiness/Resistance -- +6 to Armor/Magic Res.
And Meditation -- +3 Mana per 5 (I believe it is now.)

The first two, in combination with my rune set up, usually means I can tank more than enough for early game laning. The extra mana regeneration is very nice to have as well as it encourages and allows you to use more abilities throughout the game.

I think this is a pretty standard skill sequence to use for Rammus because his Puncturing Taunt is amazing, some might say even OP~! Maximizing taunt first is always helpful because you can pull enemies into towers with it, prevent them from using spells, and keep them away from an ally.

Defensive Ball Curl is also what helps Rammus do what he does best, tank. It adds 50 + (25 per additional rank) to both his armor and magic resistance temporarily. It also is very nice to use because of it's retaliation effect, causing attackers to take a set amount of damage back based on the current amount of armor you have. *As a note I highly doubt the armor gained from this effect adds into the damage reflected*

Powerball, just keep on spinning. Powerball is quite obviously great for getting from point A to point B very quickly, adding a little bit of damage and a slow in if point B happens to be an enemy. The slow effect on hit is handy for keeping up with targets for a few seconds before having to taunt them in place. On hit, powerball also knocks the target just an inch away, breaking channeled moves and acting as a way to nudge them twards your allies. If I can Puncturing Taunt an opponent first, I'll save Powerball until it wears out just so I can keep them knocked in place for another half second from the impact and have them slowed afterwards.

Tremors, a small but effective area of effect damage spell. This spell is probably the best way for Rammus to get any good farming done next to Defensive ball. It's relatively short cooldown makes this spell quite handy to use for nearly all combat situations: big minon hordes, team battles, one on one, or even going for tougher neutral minion's/dragon, it's a wonderful ultimate to have for everything but tanks, it won't do too much there.

Playing a Tank Rammus, you primarily should try your best to keep any of your squishier team mates from being focused down as much as you can obviously. Use Taunt to keep key enemies from using abilities that could devastate your team like Fiddlestick's ultimate for example. Taunt is also great for getting enemies in position for your teammates or keeping them where they are. (It's fun to center targets in the middle of Pantheon's ultimate.) On another note, it's best to focus down fed enemy players! Take the damage from them for your team!

If you want you can change the Reverie with Warmog's armor or with Guardian
Angle for more armor and if you die to resurrect and tank a little bit more for your team.
At the begging of one of my games i died 7 times but when i made that build
complete i made a 4 kills in a row and still have 60% of my blood.

From LoL database:
Attack Range: 125
Health: 420 (+86 / per level)
Mana: 255 (+33 / per level)
Move Speed: 310
Armor: 21 (+3.8 / per level)
Magic Resist: 30 (+0 / per level)
Critical Strike Chance: 4% (+0.2% / per level)
Health Regen: 1 (+0.11 / per level)
Mana Regen: 4.5 (+0.06 / per level)

Level 18 Stats:
Health: 1986
Mana: 849
Movement Speed: 310
Armor: 89.4
Magic Resist: 30
Critical Strike Chance: 7.6%
Health Regen: 2.98
Mana Regen: 5.58

In other words:

Powerball (PB)
Defensive Ball Curl (DBC)
Puncturing Taunt (Taunt)
Tremors (Trem)

1) PB
2) Taunt
3) Taunt
4) DBC
5) Taunt
6) Trem
7) DBC
8) Taunt
9) DBC
10) Taunt
11) Trem
12) DBC
13) DBC
14) PB
15) PB
16) Trem
17) PB
18) PB

Rammus' unique abilities make him the best Armordillo in the game to attack enemies playing pansy under their turret. He has PB to get in and out of turret range quickly, DBC to last underneath heavy turret fire, tremors to hold aggro, and taunt to prevent the enemy from escaping. As long as you understand how to properly manipulate turrets, you will find that Rammus takes towers and their precious cargo like the port authority takes Gangplank's exotic fruit and contraband.

Riot has patched to target the first champion that triggers a call for help and not switch until he leaves turret range. It means that Rammus lost one of his big advantages as a tank. Before he was one of the few that could keep constant aggro... now anyone can do it. Just remember to get turret aggro before any of your allies and pop DBC and you'll be fine. That also makes this section almost a universal guide... use a similar strategy with any tank you play.

So here's how to effectively destroy an enemy or group of enemies turtling underneath their turret:

1) Assess the situation. Do some mental calculations on the number of hits you can take compared to the amount of time it will take for you and your allies to kill all the enemies under the turret and get out.
2) Mark your first target (ping the squishiest) and alert your allies that you are planning to tower dive, and ask them to ignore the fact that there is a turret there. That's your worry.
3) YOU MUST GET AGGRO FIRST. Use No Flash initiation on the enemy you pinged. It often works well to PB in from behind just before your team charges from the front. Quickly taunt the target and turn on DBC.
4) If the turret is near death worry more about keeping tremors on that. Tremors isn't needed to keep aggro so use it as the simple damaging spell that can kill turrets that it is.
5) Make sure you get out when you get low. If you are under 35% without DBC on you should normally be hightailing it out of there with your allies (of course this depends on game stage).

Hopefully by the time you are forced to get out of turret range your team will have decimated the enemy by surprise and you will be able to run out with no casualties. This is a trick you will be able to use with relative ease once you get the hang of it.

You are the tank. You are the impenetrable ball, the epicenter of the earthquake that will rock the enemy. In a teamfight you have a few jobs. You must be the surprise initiator into the back of their team, knocking as many as possible. You must disable their strongest dps, either magical or physical, until your team can burst him dead. You must cause maximum AoE damage while the rest of your team files in. You must not die until their team has been decimated else you risk your whole team dying. Because nobody remembers what they read in paragraphs, let me put your basic sequence in a nice, ordered list.

1) Ping a group of enemies, and tell your allies that you intend to head in to mow them down.
2) Pull a bold, unexpected Powerball initiation into as many of their team as possible (make sure your team is following you).
3) Turn on Tremors and position yourself in the center of their clump.
4) Turn on DBC so that you'll live long enough for your team to file in.
5) As soon as their strongest DPS moves to attack a squishy ally of yours, taunt and ping him.
6) For as long as your Tremors is up, try to stand near the biggest group of enemies. They will often scatter away, so try to follow the group of 2-3 that runs in the same direction. If you are forced to choose a single enemy then follow after their dps (he will run away as taunt wears off).
7) If you fall below 15% health, attempt to waltz out of the fight during the mayhem ( Flash out if it's up). If you can make it out you can then be helpful after the initial clash. Stay a little ways away until you are needed to save a fleeing ally or chase down a fleeing enemy.