You should pick Rammus if your team needs tankyness/CC, or if the enemy team have a hypercarry such as Master Yi, Kassadin, Twtich etc. as Rammus is really good at shutting them down. He is generally better against squishier teamcomps and teamcomps with lots of AD champs.

Pros
- Extremely tanky
- Amazing ganks
- Amazing into AD comps
- Can almost 1 shot an ADC if ahead
- Good engage
- Strong at all stages of the game
- Still has utility if behind
- Healthy jungle clear
- Good escape with Powerball
- Mechanically easy

Cons
- Slow objective clear
- Relatively slow jungle clear
- Has a few pretty bad matchups
- Very weak against tanks

- Don't W while in your Q as it will cancel your Q
- However, you can cast your R while in your Q
- Be sure to use E and W together as your attack speed bonus will last longer
- Buy lots of control wards
- Make sure you peel for your carries
- Always target the most fed enemy
- Tank tower shots for your teammates to utilize your tankyness
- Ping your bot lane to help you with drag as Rammus struggles to solo it quickly
- Take Oracle Lens to clear enemy wards, and especially into invis champs like Evelynn and Kha'Zix

Flash - Good for escaping, engaging, or flashing over the enemy frontline to their carries while in your Q. Ghost can also be viable in some situtations.

Smite - An essential spell for jungle.

Thornmail - The core item on Rammus as it synergises perfectly with his kit. Rush this item straight after you finish Cinderhulk.

Dead Man's Plate - A good choice if you want more out of combat movement speed. Right now it's a relatively weak item, though.

Gargoyle Stoneplate - Probably the best teamfighting item on Rammus as it gives an incredible amount of tankyness and will let you survive any teamfight.

Abyssal Mask - A strong item if your team has lots of magic damage.

Adaptive Helm - Strong against AP teamcomps and champions such as Teemo, Katarina and Cassiopeia

Warmog's Armor - A reliable item if the enemies have little or no max health damage. This will let you stay around fights without having to back as it gives lots of healing while out of combat.

Randuin's Omen - A must have against crit champs such as Tryndamere, Jinx, Yasuo etc.

Aftershock is an essential rune on Rammus, anything else is simply not as good.
Conditioning is also essential as Rammus scales with armor and magic resist.

You can either go Font of Life and Unflinching or Demolish and Overgrowth, it just depends on your playstyle.

Font of Life is good as it heals your teammates when they attack the same champion as you. Unflinching is good into teams with lots of CC. Also remember that tenacity doesn't affect knockups.

The Demolish and Overgrowth combo is for when you want to help your lanes push. Demolish will help you and your laner kill towers quickly, and while you do so you will gain max HP from the deaths of nearby minions because of Overgrowth.

In terms of secondary runes, Cheap Shot and Ravenous Hunter are the highest winrate runes at the moment. Cheap Shot gives you a bit of extra true damage to help you burst down squishies, and Ravenous Hunter will give you a little bit of sustain in the jungle and will help you stay healthy in fights once you've reached 5 stacks.

Triumph and Coup de Grace are also completely viable. Pick these runes over the domination secondary if you want to have a bit more healing in teamfights and skirmishes.

The main path I like to go is Red, raptors, wolves, blue, gromp, scuttle. This is a reliable path if you don't want to have to fight the enemy jungler at scuttle. Rammus is only average early game, so there are a fair few matchups where he loses early, such as Olaf, Volibear and Xin Zhao. With this path you can do krugs before raptors but you risk the enemy jungler getting both scuttles.

You should take raptors and wolves as much as possible, as Rammus has very good AOE clear because of his W Defensive Ball Curl. Also keep in mind that krugs are the most valuable camp in terms of gold and XP.

There are many different paths for all junglers, including Rammus. Just try out whichever works for you, as there is no single best path. It will vary depending on your playstyle and the champion you are up against.

Rammus has really good ganks as he has his Q for a lot of movement speed, and he has lots of cc. However, one thing Rammus lacks is damage. For this reason, you'll be better off ganking lanes with a lot of damage so that you can actually secure the kill, for example Zed or Katarina. If you're ganking a Maokai top lane, you will most likely not even get a kill or a flash, as you and Maokai will not have enough damage (unless the enemy top lane is already low).

Alright guys, hopefully you learned a thing or two from my guide. Thanks for reading and just remember than any feedback is greatly appreciated :)

cya :3