I wrote this guide for my friend who is our team's designated jungler in 5v5's. I will freely admit that I currently play at low ELO (my 700+ wins in normals take up a lot of time), but this guide is not designed for people new to jungling.

Anyway, this is a Tiger Stance-based jungle because Tiger offers better burst damage and therefore more explosive ganks. As with any champion, the key to success is practice. This guide is simply an option for a very versatile champion

Phoenix may be my new favorite. See Updates.

Patch 1.0.0.124
Reduced health and mana gain from Turtle Stance. It hurts a little, but you just have to be a little more mana conscious.

Other updates: I might start maining Phoenix over Tiger. The jungling/farming ability of Phoneix is just amazing. You clear camps/waves like nothing, and have great sustained damage. Plus, Madred's Bloodrazor has crazy dps.

Pretty standard runes. The AD reds are for more tiger damage (since you get an AD-based proc as well as AS), everything else is pretty self-explanatory.

Update
For both Phoenix and Tiger, use MS quints. You gank better and have a better game overall, because Udyr's only gap closer is his speed.

Masteries, at least for Udyr, are pretty variable because he is such a strong jungler. I've looked at a lot of guides and modified my own masteries based on their advice, and you can feel free to do the same. The reasoning behind my own set is:

Offensive Tree:
Improved Smite - a little extra gold and reduced CD for faster jungling
15% magic pen - increased damage mid-late game. I don't want my damage to start falling off against tanks, so this is pretty much required if you plan on building Bloodrazor. The damage from Tiger and Phoenix is also magic, so I want those to maintain some of their damage.

Defensive Tree:
Armor - pretty self explanatory for a jungler, and especially useful since we don't start with a cloth armor
Nimbleness - Udyr may not be dodge-based like Jax, but he can still dodge enough to make this extremely useful.

Utility Tree
Increased XP - vital to faster and safer jungling, and also earlier ganking
Improved Buff Duration - pretty much says it all

Phoenix Masteries
I very well may change this for my Tiger build as well, but I haven't tried it. I would also recommend trying a more standard 9-0-21 set up, but I haven't tested it yet. The idea is that you want 15%mpen because a LOT of your damage is magic, 3%MS because you will have 397 MS with level 1 boots (with quints of course) making you scary fast with bear ganks. I'm guessing the 6 armor is unnecessary.

Just as I take AD reds, I start with Long Sword to increase my Tiger damage and speed at which I jungle. Plus, Udyr only needs 1 health potion to jungle safely. Get wards when you can, since you are the jungler and have a duty to protect your lanes. The build is a pretty standard Trinity Off-Tank build, centered around my favorite item (Trinity Force, obviously). I'm not going to discuss the pros of the Holy Trinity here, just know that it is one of the best items on a Tiger-based Udyr.

As to the item sequence, if you are a truly good player you will know that there is not always one sequence. Sometimes I build an early HoG if I do very well early game and want to ramp into late game items faster. Other times I get Phage before Sheen. Look at how you, your team, and the enemy are playing and build according to each game.

Other Items:
There are, of course, many other items that are amazing on Udyr. I generally avoid Frozen Mallet because it is very expensive and I prefer Trinity, but it is a viable choice. Warmog's+Atma's can be very scary on Udyr, but again it is quite pricey. A optional choice to the last item is Youmuu's Ghostblade. It has amazing synergy with Udyr and Trinity Force. If you prefer DPS over tankiness you can also take Wit's End over FoN.

Phoenix Items
Phoenix gets early attack speed and then builds tanky. MBR just does crazy damage to people with low magic resist, plus it gives attack damage and armor. The rest of the build is the same.

This is one of my favorite parts about Udyr. He has no ult, so instead of becoming a much larger presence at level 6 he is a significant presence at all levels. Lately I've been ganking at level 3 which is why I get Bear Stance then. If you're going to get red buff before ganking, take a second point in Tiger at level 3 and then get Bear at level 4. The second point in Turtle is useful for jungling after you gank and for when your blue buff runs out. After that, the sequence is about as variable as the item build (although I do recommend getting at least 4 points in Bear because it is Udyr's only way to close gaps).

Phoenix Skills
Same mentality with Tiger for the most part, just leveling Phoenix instead.

Smite - take it or everyone will call you a n00b. Because you are one if you jungle without smite.

Flash - What else is there to say, besides the fact that there is a reason Riot is thinking about a Flash rework

Other Choices:
Ghost - If you want Ghost instead of Flash, go for it, I can't stop you. But just remember that it doesn't synergize that well with other MS buffs because there is a MS soft-cap at 500.

Exhaust - I guess it's possible to take this, but I would much rather have Flash or even Ghost.

And now for the point of this guide. The jungle!

My current standard route is: Blue Buff -> Wolves -> Wraiths -> Gank

Remember, ask for a leash if you start at blue! After you kill the Wraith camp you will be level 3 and can get a point in Bear. If mid has harassed the enemy a bit they will generally be low enough to kill if you position correctly. Otherwise you can gank a different lane.

The other option is: Blue -> Wolves -> Wraiths -> Golems -> Red (?) -> Gank/Buy

This is another time when everything is variable. Jungling is all about balancing your farming with helping lanes. Sometimes you just run around ganking people who overextend, other times you counter-jungle. Udyr may not have a super cool counter-jungle ability, but if you catch the enemy jungler you will pretty much always kill them if they try to fight you. Udyr's jungle options are wide open since they buffed his mana costs. He no longer needs the Blue Buff all the time, so you can wander wherever you want as long as you always leave enough mana to switch to Turtle Stance and regen mana/health.

Phoenix Jungle
I start at wraiths, smiting Papa wraith. Then wolves and doubles (smite should be off cd for this camp). Go heal, come back with your cloth armor + pot, then clear the jungle starting at blue buff. Proceed to gank/jungle/etc as necessary.

TL;DR
Udyr is a very versatile champion, and as such, a competent player will play based on the situation in each game. Beyond that, just as with any champ, practice will help you to understand how to position, how/when/who to fight, stance sequencing, etc.



Good luck and have fun with Udyr! And, as always, respectful/useful comments are appreciated!