Filling the tear with the bloo
Not Updated For Current Season
Always start with Hunter's talisman and start at blue or you will run out of mana very soon. Udyr has fantastic health sustain but mana is sometimes a problem, so we're going Refillable into Hunter's pot.
Finish Skirmisher's, then proceed to rush tier 1 boots and Hunter's pot. After that finish Devourer, then buy Tear and Swifties. After that whether you want to rush Manamune or leave it at Tear for a while is up to you. Manamune gives you more instant power and stacks a bit faster but isnt as strong as rushing Iceborn asap.
1. Udyr stacks Tear extremely fast due to him spamming his stances all the time
2. With Iceborn+Tear you never run out of mana
3. Muramana+tiger gives Udyr extremely high damage output
With the change to Muramana not requiring you to constantly togle it on and off it's much easier to manage even with bit worse macro management skills.
Rest of the items
So I always go Devourer, Manamune and Iceborn. Usually Swiftness boots but occasionally Mercs are better, if the enemy team has a lot of hard cc and/or magic damage.
Almost always my 6th item is Zz'Rot thanks to it's amazing map pressure. 5th item usually is Dead Man's plate but sometimes Visage (enemy has a lot of magic dmg) or Thornmail (lots of auto attackers like 3 adcs) are better choices.
Always start leveling Q->W->E. Always max Q first, but whether you want to max W or E second is up to personal preference.