Hello!
Im high plat (Platinum 2: 70LP at the moment) player playing mostly Volibear and this is my guide! I have ~300 volibear rankeds from season 3 and ~150 volibear rankeds in season 4 so far. English is not my native language so don't get too mad about spelling errors ;)

Why Volibear?:
Volibear is strong damage-dealing tank. Volibear excells at initiating teamfights with Flash fling and peeling/kiting for your carries. Volibear has huge burst damage when you combine your fling + E + couple auto-attack + botrk active and execute W. Meanwhile destroying opponents squishies you can survive massive amounts of damage with your passive combined with buffed Summoner Heal.
Volibear is played rarely and many dont seem to know how to play against him. Volibear's burst damage seems to always surprise lane opponents and this leads to winning lanes very often. Good tip is to extend a trade so that your opponent think's you have made a mistake and over-extended. Proceed to nearly "die" -> passive starts to tick -> opponent ignites and thinks he gots you -> Use summoner Heal -> Opponent realizes that he has lost the trades and you finish him easily with your W. To do this you must know Volibear's limits and your opponents damage.

Flash is your must-have summoner spell since it will be your main initiating tool.
To top lane (at 4.5) I suggest you to always take Heal. Since Heal reduces all healing reduction effects it works great with your passive since nearly everyone laning vs Volibear takes ignite.
Teleport & ignite are optional. Maybe at 4.6 if rumoured heal nerfs go through you should take something else.

Pros:
+Naturaly tanky with summoner heal + passive

+Very good initiation with Flash

+Surprising burst damage

+Execute ability, good at securing objectives

+Good at turret diving and baiting a turret dive

+One of the best killstealers in game.

Cons:
-Very squishy early game

-Very voulnerable to kiting

-Weak laning if opponent knows how to play vs Volibear

-Hard to master

Volibear's base attack damage is extremely low which makes farming very difficult. To make it easier you need to PRACTISE.
Practicing farming:
1: Go to custom game with no opponents. Take Volibear with blank rune page and blank mastery page. Dont buy anything at the start of the game.
2: Try to get 100% of the minions each wave. You will notice how difficult it actually is without runes.
3: Play 20 minutes and try to get better each wave.
4: Repeat.
After couple spent hours:
1: Go to custom game with 3 bots against (1 will go to each lane)
2: Take volibear with runes and masteries and build normally.
3: Try to get 100% last hits each wave while pushing bots away from lane.
Note: Do not kill bots, just push them away from lane.
4: Push turrets and take minions as well as you can.
5: Repeat when you've reached inhibitor.

Laning as Volibear is a bit difficult compared to many other top laners.
If you are facing