Trundle is a great Twisted Treeline jungler. He jungles quickly and is quite safe doing so. He can counter-jungle with decent effect. He can chase with Contaminate, run away with Pillar of Filth and also gank effectively, I find he as strong as a jungler as Nunu in Twisted Treeline.

In this guide, I'll go over how I find Trundle to be effective, just remember that runes, masteries, and items are not set in stone, as you develop your own style of gameplay, your items may very well change but I do find these items very effective against a variety of team compositions but not all.

As explained above, these runes are not set in stone, Armour VS Dodge for seals is extremely based on preference, I prefer armour but you may have/like dodge, by all means, take them if you choose.

9 Armour Penetration Marks

I find these to be the best, it's pretty obvious, I doubt anyone will take something else. You need these to keep your damage at it's fullest.

9 Armour Seals

Seals are for two things, mana regen, and defense. Trundle should have no problem with mana except you may find you run out of mana late game if you are sitting at 2000 gold because you haven't been back for a long time, since you don't need mana regen, defensive seals it is! Now some people say dodge, some people say armour, both have a pretty even effect in the jungle, the only difference really is your opponents. Armour can be countered with armour pen, dodge cannot. However, skills that dish out physical damage aren't affected by dodge, but armour does affect it, thus armour would help more against someone like Pantheon, but Master Yi on the other hand, has no physical damaging skills, thus dodge would probably work better against him.
tl;dr
Dodge counters Yi
Armour counters Pantheon
Really doesn't matter which one . . . Preference!

9 Cooldown Reduction Glyphs

Glyphs don't do much for trundle. Cooldown reduction is probably the best for him as A) Workes nicely on all champions, B) Almost everyone has these C) What else would you pick?

3 Health Quintessence

Quintessence, the rune that maximizes your playing style!
Health quints are probably the most commonly used on all champions, but quints are very dependent on your preference. Personally I use EXP quints, I like to keep up with my teammates, one of the reasons to have a jungler is have the team benefit from a larger amount of EXP. Movement speed is also a decent pick, keeps you agile, will help you kill, run and help you clear the jungle faster.

Another personal preference. I prefer 21/0/9. The only necessity is in the Utility. You need the extra EXP UNLESS you took EXP quints, then getting some defensive masteries might be an option for you.

I like to take improved smite since I don't need AP, mostly a filler but it does give around 5 extra gold every 75 seconds or so. (Not much if you think about it) but the cooldown reduction on it is nice. I also usually take improved ghost, mostly as a filler, but it's more speed so you run faster than your chasing/fleeing opponent who is also using ghost. (Or at least he wont run faster than you from having it himself.)

Again, really a preference, but I suggest at least 21/0/9.

Start of your game with the typical, Cloth Armour and 5 HP Pots. (You can try 2 HP pots and a Ward, although useful, you may find your HP drops low at some points, if someone passes you, you can easily die.)

You will probably be out in the jungle until your ready for the Madred's Razors. If you have enough gold, grab your boots too.

After jungling, most games, you shouldn't be back until you can finish off your Wriggle's Lantern. I suggest this over the Bloodrazors because, you'll be in be in the jungle, team fighting or pushing. This items helps you push, jungle and has some lifesteal for teamfights. It also gives you a useful ward to keep tabs on Dragon or Red, Dragon and Red are yours, don't let your opponents take these from you! You'll also be fairly short on AS the whole game so Bloodrazors is way to expensive to just use the stats without the passive, since it's only good on high AS champions and against beefy opponents, lastly, you don't have the Magic Penetration to utilize the damage effectively.

It's just been brought to my attention that a Sheen is a great item to take, I completely agree with this. The Sheen is fairly decent on gold and gives you a good amount extra damage. Now you may be thinking, a Sheen is good? Does that mean a Trinity Force is better! Well, not really. I would be pretty impressed if you can cram it into the game after a Frozen Mallet. But if you're getting all the dragons, a good amount of kills/assists and jungling is going smoothly, try it, see how you like it.

Later top off your Merc treads, these work hand in hand with your contaminate, huge amount of CC reduction! You > Sion, You > Taric, You > Kennen, You > CC. Grab Ninja Tabi if they are low on CC and/or have a lot of AD.

After this, you should work towards a Frozen Mallet, it keeps your opponents from running, keeps you alive and allows you to dish out tons of damage. Average games should end about here but if it's taking this long, the rest of your items should be extremely situational, but a few items may be, Bloodthirster(General damage and survivability), Sword of Divine,(For Jax)
B.F. Sword, etc.

You may find that there is an item you like that you usually replace over one I take, by all means, do it! This guide isn't meant to hold you back, it's meant to get you going, modify, adapt to your enemy and troll to the end. (When I say troll, I mean troll by pwning them, not by feeding, leaving, being distruptive) ^_^

You simply must rank Rabid Bite, it's your bread and butter, more damage. Damage heals you in camps, levels you, gets you kills, everything you need in LoL! So now it's Pillar vs Contaminate. I prefer Contaminate, gives you more damage, gives you a bit of survivability with reduced CC, movement speed for chasing, all those lovely things. The pillar's main use in Twisted Treeline is the actual pillar, not the slow, putting up a pillar can completely block pathways in Twisted Treeline, why slow them when they wont even go that way?

Basically, it's obvious, Rabid Bite > Contaminate > Pillar.

Smite is a must, if you don't think so, wrong guide, leave now before you become even more lost and confused.

I prefer ghost to the rest. Everyone has ghost, so how do you catch up if you're the only one without it? You'll lose your team, your opponents, get hunted down, get ran away from, all that.

Ignite is a decent pick but it makes really early ganks completely expected, they'll be on their toes, with their cursor ready to Flash>Ghost out of there.

Exhaust is nice, it helps with fights all the way through, this is my go to, summoner if there is a good reason not to take ghost.

Pros:
-Random, more frequent ganks.
-Increased EXP for all teammates.
-More powerful Red and Dragon control.
-Strong early and mid game, very rare to get past mid game.
-Out does many other Twisted Treeline junglers. Rammus? Drops down to like 200 HP in the jungle.
-Fast jungling
-+1 To trolling (I do not consent trolling, I am strongly against trolling, unless it's just the super gank and winning kind)
-Ganks HARD.

Cons:
-Needs to snowball a bit, dying early game and having their team have you running from the jungle often will result in a loss.
-Sometimes your 2v1 laner gets badly beaten, gives First Blood and may even feed, causing you to have to lane with Smite... It sucks.
-Smells BAD.

Get your cloth armour, pots and get you and your team to the bottom camp near the red fast, you need your whole team there, if their team comes along and you're sitting solo, Trundle just trolled his own team, well, they trolled you with their ignorance!

Play it smart before the minions spawn, sometimes you need to wait a few seconds for the enemy to appear on the map, just make sure your team either goes to their lane, or waits near red while you actually start killing.

Pop an HP pot as your start with the first camp, start with Rabid Bite(Q) but only use it when the buff from it is gone, or you will run into mana problems.

Once you finish, quickly head upwards. Get to the top camp, but DO NOT FIGHT THE BUFFS. Kill the double golems or the three wolves (Not the buff wolves) continue to only use rabid bite for the buff.

Now it gets situational, does the top lane have a 100 HP opponent, kill 'em. Does your teammate have 100 HP? Lane while he goes back. Is their whole team MIA? Lane with top for a few, but stay near the turret. Is their whole team visible? Go to the opposite side of the top jungle to kill their small camp.

Once the first camp you started with spawns again (Should be about after you get your third camp if you didn't gank or lane) go get the bot jungle small camp. Continue hitting these camps for a while but remember, GANK, LANE AND HARASS. Get in 200 damage on their top? Looks like your teammate has the advantage now. Killed someone? Good! Died? You shouldn't have.

Keep your eye on the mini-map, do not rely on MIA calls. It could take Sion less than a second to flash into your small camp, stun you, blow his shield and finish you without you knowing what happened.

The second you get your Wriggle's ward red, maybe even kill it, but make sure it's safe, and when you do, pull it closer to your side.

Mastering the jungle is mastering improvisation. (Oh, and map control!)

You should be ganking non-stop, the whole game, jungle, gank jungle, gank, push, gank, gank, jungle. Be unpredictable. As the team, you're HP/AD. This means you should be diving into the action, right after your tank goes in. Protect your squishy! Tank protects you, you protect squishy, squishy kills all. If you see someone passing through the jungle, call it out, did someone recall? Call it out, someone bot is MIA and your teammate hasn't called it? Call it out. Your eyes should be on the mini-map a lot more than your teammates, if all three are on the mini-map, in the lanes, you can't be ganked, so keep staring, the neutrals aren't gonna behave randomly so you don't need to watch them.

WARDS! Your job to ward a decent amount, mostly from Wriggle's but you probably should have bought another ward or two throughout the game.

At level 6-7, you can solo the dragon without issues and pretty fast too. If all three are bot and your two allies are bot, AND THEY ARE OKAY. Solo the dragon. Or maybe top just recalled, and YOU SAW THEM DISAPPEAR, you might want to try it. Keep your brain with you, don't try when all three are top, or if you saw one enter the top jungle.

Getting red is pretty fast, fairly safe at times too. If your solo has pushed up the bot lane past the middle of the lane, and all three are in their lanes, it's a decent time to get it, if your bot lane is a ranged carry, give it to him once it's almost dead. Otherwise, drag it over, closer to your side.

If your team just aced fairly early game and the respond times are still low, the minions are pushed to your side, don't push, dragon, even grab red if you can.

This just about sums it up to my jungling Trundle. I hope you enjoy trollin' it up in Twisted Treeline. Just remember, common sense beats any guide, any day. This guide is not set in stone, I encourage you to shape and mold it to your preference.

I spent my time to help you, please return the favor, rate it, comment, maybe even tell a friend. But a minute of your time commenting, sure doesn't beat the time it took for me. ^_^

Enjoy!

~EnduringInsanity

I will definitely add more colour! I love the appearance of colourful guides.

Suggestions will be considered and acted upon based on how I feel.

I will format it and organize it.

Search for spelling errors, (Wrote this at night while I really should be sleeping.)