Hey Guys, this is my first guide, I'm from Germany, so please excuse some written faults.

I hope you all enjoy it and everybody can learn something new about

Udyr is a Champ, which is playable on a tanky way or an aggressively way, so he is very balanced. I prefer the balanced way between a 1-2 damage items and 3-4 defensive items.
So lets learn something new about Udyr ! :)

Pro's
+fast jungle clear
+surprisely fast ganks with Q Wilding Claw
+great sustain in jungle with W Iron Mantle

Con's
-"no ultimate ability"
-you need much training, experience for doing successfull ganks
-mana problems before Trinity Force or Iceborn Gauntlet

Hunter's Machete
THE S3 jungler item
Boots of Swiftness
Faster moving across the map [a fast Udyr is always scary!]
Blade of the Ruined King
AD, AS, LS, Slow (Are there better items in this game?)
- Buy it, if the enemy team is very tanky 'cause the active effect is very good for ganks. (Steal 15% of their maximum health ans slow them.
Spirit of the Ancient Golem
CD, health and mana-/health reg. are good 'cause you can spam your E for chasing/ganking and mana reg. is good for Udyr 'cause he actually has mana problems in early/mid game
Sunfire Aegis
Health, armor and AoE magic damage good for more sustain in teamfights and actually you do bonus damage too
Iceborn Gauntlet
After finishing this, you haven't mana need anymore and you'll have more CD, armor. This item gives
an AoE damage and slow (OP)
These are the "must have's"
Now you have too decide which item you take for your last open slot! (Example's Top)

Smite
What should I say? It's the most IMPORTANT summoner spell you need. It's like no jungler without smite. It's also important for secure dragons and barons.
Flash
I take it with me every game 'cause it's very flexible. For example, if your team starts a teamfight and you as Udyr are in the middle of it, but you realize that you are going to loose it, you have to come out very quickly now. Use Blazing Stampede to run away and use Flash over a wall so it's difficult for the enemy to chase you.
Or if you want to gank and you are sure that you can kill him with your Toplaner for example. Flash while using Blazing Stampede for a big surprise moment and kill him now.

Here I'm explaining you guys my normal jungle route:
So at the beginning you look who is your enemy's jungler. If it's a jungler like Rengar who normally starts at red, you start at red too. But at 1:40 you make the wolves/wraiths. This only works with a smiteless red/blue buff.
After getting your smiteless buff you reach level 2, now u skill Blazing Stampede and run instantly to your enemys other buff. So when u started at red you run to the enemys blue and conversely. Hind yourself in the bush next to the ancient golem/ lizard elder and wait for the enemy jungler.
Now you have to decide, either you try to steal it with your smite but for this you must have a perfect timing, or you wait till he finished it (now he normally is very low life) and you just kill him, he normally can't get out this situation 'cause your stun hold him and you kill him with your Wilding Claw or Wingborne Storm, depending of your playstyle.

As jungler one of your missions is to ward. And as a counterjungler like Udyr it's important to know at which times and at which places you have to ward, for being a successfull counterjungler.The green circles are places for Vision Ward. Now you can see if the enemy team warded dragon and baron too. Try to hold these wards on all the time 'cause the dragon baron nashor are important.
They bring your team:

Dragon and Baron giving you and your teammates a lot of money.
Baron brings you a special buff, which increases your AD and AP for example.

The red circles are just sight ward and are important for stealing the buffs away from your enemy.
You should set the first ward at 7:10 at the buff who the enemy jungler was starting. At the next 10 secs the buff respawns, be there before your enemy arrives and take it FAST!

A short list of Champions which can make problems:

Ashe counters Udyr hard 'cause of her slow it's hard to attain to her.
With Kayle's Q it's like the same. BIG SLOW
Janna can throw her tornado on you so you'll stopped too.
The same with Trundle, his E is a big obstruction and all around you get
slowed very hard.

And now a short list of Champions you can counter easyily:

Udyr works just amazing with every champion with good cc, 'cause every time you'll gank and you have a champion like Blitzcrank or Ahri in your team they can just use Rocket Grab or Charm and you'll have enough time to run with Blazing Stampede and stun the enemy = easy kill.

Here a list of Champions which are perfect to play with an Udyr:

As you can hopefully see, every champion in the example above has one ability to "stop" enemys running away.

So this is my guide to be successfull as Udyr. I try to update it after changes as fast as I can.
I just want to say "thank you"! for looking and reading my guide and I hope you acquire some tactics for playing Udyr.
Leave comments if you have any questions or if you wish to know something. I'm going to add more informations.
Now I wish you have a good time with Udyr the spirit walker :)!