Welcome to my build!
First off, I know it's not going to look real pretty and all, I don't have the time to look at jhoijhoi's how-to in depth. I just wanted to show you all my ability sequence and item build that I've found extremely useful when playing Volibear.
Why play Voli? Here's a few reasons:
Passive makes Mundo cry
Frenzy makes Garen cry (IMO)
Keeps enemies from running away
Fun to play
Great KS ability
Giant Lighting Overpowered Pawner (GLOP)
So first off, I choose from either Ruby Crystal or Doran's Shield. Doran's gives you a good start-off with armor and health regen, but Ruby Crystal will help make your passive and Frenzy more powerful, and can quickly be built into two items you will grab later (Warmog's and Spirit Visage).
After that I grab Mercury's Treads almost always. They are my favorite boots and will give you early game magic resist but most importantly Tenacity.
Now you need to choose which path to take. If they have lots of magic resist, grab Spirit Visage for health, magic resist, and cooldown, as well as a buff to your passive. If they're going AD, grab Frozen Heart. It will solve your mana problems for the rest of the game, give you great cooldown and armor, and slow enemy attack speeds. If you have enough money for a Giant's belt, then grab Warmog's.
If you chose Frozen Heart or Spirit Visage, grab the other. If they don't have any AD or AP, then instead grab Warmog's now. If you got Warmog's, try to get these two.
Now this is where my build isn't as solid, because I rarely reach this point. When you decide to grab more damage, get Last Whisperer. You'll be more offtanky now and can rip their tanks.
Aegis of the Legion is good for buffing your allies.
Randuin's is a great anti-carry item. Don't forget its active!
Force of Nature will make their AP cry like a baby, and give you nice move speed to help catch up to them.
Need more health? Grab another Warmog's to make your Frenzy more powerful.
Still having CC problems? Banshee's Veil or Quicksilver Sash will solve it.
Frozen Mallet is good on Volibear because of extra damage, health, but mainly the slow it gives. Volibear has trouble keeping enemies close enough to him, but this will help solve the problem.
Last Whisperer is good for extra damage and armor penetration if you want to deal more damage.
Atma's Impaler and Warmog's are good for more armor and damage. For those less-savvy out there getting an Atma's Impaler and Warmog's is known as Atmogs.
So the core of this build is:
Ruby Crystal will allow you to build more quickly into Warmog's or Spirit Visage.
Doran's Shield gives good early game survivability
Shoes + pots speed and survivability w/ pots
Armor + pots better survivability
Additional items I would recommend:
Force of Nature for movespeed and magic resist
Atma's Impaler for more basic attack damage and armor
Last Whisperer for more damage and armor penetration
Frozen Mallet for more health, attack, and the useful slow.
Aegis of the Legion for supporting allies and extra stats.
Ninja Tabi when playing against few CCs and more carries.
Boots of Swiftness if there's low CC and you feel like you need to get around faster.
Now for Skills:
His Passive is really good to help you survive at low-health. Combined with heal and you can be really deceptive. Don't forget that if you feel you need it popped up before you go into a battle go jungle and let the monsters lower you to that point. This is useful if you're low health against bursters.
I grab Majestic Roar first. I know other people like to grab Frenzy, but I feel that it helps get early kills better because of what you'll get at level 2.
Next grab your crazy bear charge, Roaring Thunder. Surprise the enemy by popping them into your tower and use Majestic Roar to keep them there.
NOTE: On Summoner's Rift, your frontline towers are surrounded by grass. If an enemy is at where it's rocky but just reaching the grass, then your Rolling Thunder will be able to pop them back from there.
Now max out Frenzy. At level 3 you're good at keeping the enemy from running away and can grab an easy kill w/ your ganker using Frenzy. Whenever you can't upgrade Frenzy upgrade Majestic Roar.
NOTE: Frenzy is the best ks ability in the game. Save it for last-hiting champs when it will deal the most and almost always get you the kill.
Your ult, Thunder Claws, is good for dealing extra damage, especially in teamfights and enemies who you don't have to worry about running away. I haven't really gotten the hang of it, but just make sure that you can hit them w/out them running away too fast. Max it whenever it will let you.
So, for reaching an enemy, use Rolling Thunder, then Majestic Roar, and save Frenzy for when they're low health (say 10-15%). Use Majestic Roar if you feel you need the extra damage and the enemy is going to commit. You can also use flash before Rolling Thunder so that they can't run when they realize what you're doing.
For summoner spells, I always grab Flash. It's a great escaping tool.
You can get heal for when your passive isn't around, and when you need to heal teammates in a teamfight. It's also useful for using once your passive pops up so people can't burst you down. It's also good against early tower-divers.
Ignite is good to lower enemy lifesteal and such and get early game kills, but I'm not too fond of it.
Exhaust is a great anti-carry, chasing, running ability. I recommend this over Ignite.
Clairvoyance if you feel you need to support more.
Smite if you are going to jungle. Always grab smite if you jungle, no matter what character.
For farming, remember to last hit. It can be pretty hard to do, but getting the hang of it is critical. You can use Frenzy to last-hit those big guys, and Majestic Roar to last-hit several low-health minions. If you feel you need to, though I don't recommend it, you can use your ult as well.
Team Work is very important. You need to know when your team is going to commit, and you need to get in there and cut one of their guys off with Rolling Thunder. You're a great ganker, but if an ally is ganking you're very useful in making it a success. You need to be the first one into the battle. I like to use Volibear to keep the enemy from getting away from my team. His slow and popper are useful at doing this.
It's good to always look after buying a health item to see how much damage Frenzy will do to enemies. This way you can estimate when's the best time to bite into 'em.
I play Volibear with a teammate. Ranged teammates are good, especially Ashe who can help Volibear get close to enemies. However me and my brother do Volibear and Olaf, two pretty OP characters in one lane. Olaf's axe allows me to reach them, pull them back, then slow again. Olaf's True Damage ability and my Frenzy usually pick us up at least one kill before level 6.
Success with this Build
I have not played too many games vs. human recently, but one really stands out. In one game I got 15/0 (my brother playing as Olaf got 11/0). We've had several good games recently, including a few on Twisted Treeline (where the popper keeps enemies from running under their tower).
I will try to update my success w/ this build as soon as I play some more.
Thanks for looking at my build! I know it's not really impressive, but I thought I'd just share what I've found useful with Volibear. I have not played ranked, so I don't know how well he'd fare there. Please tell me what you think, try it out, and have fun! That can sometimes be hard to remember when you play LoL if you're not doing so hot.