Your probably wondering who I am. Well my name is Ryan, and I enjoy playing League of Legends. I enjoy both summoners rift, and Twisted Treeline. Although I often play 5v5's, I have taken an interest recently in 3v3's. I made a ranked team with my friends, and we have been playing off and on in ranked 3's. Right now our team is 5-2, and I'm 4-0 while using Shyvana in 3's. I enjoy her very much, and would like to share my good information with you. This is my first guide, so please do not downvote if I have information wrong. Feel free to ask questions, and correct me if you think you should. Enjoy :D

Passive Fury of the Dragonborn:
Shyvana's melee attacks enhance her abilities.
Twin Bite - Reduces the cooldown by 0.5 seconds.
Burnout - Extends the duration by 1 second to a maximum of 6 seconds.
Flame Breath - Deals 15% of the ability's damage to debuffed targets.
Dragon's Descent - Attacks generate 2 Fury and Shyvana gains 1 Fury every 1.5 seconds while in human form.
Explanation: Incredible passive, very well thought out. Reduces cooldown of Twin Bite by .5 sec/melee hit, extends duration of Burnout by 1 sec/melee hit, deals more damage to debuffed targets with Flame Breath, and allows you to get fury.
Q Twin Bite:
Next auto attack hits twice, second hit deals 80 / 85 / 90 / 95 / 100 % of total attack damage
Dragon Form: second hit deals aoe damage in front of her
Dragon Form: Twin Bite cleaves all units in front Shyvana.
Cooldown 10/9/8/7/6 seconds
Explanation: Very good damage ability, allows you to get a lot of damage, and your passive helps your cooldown go down faster.
W Burnout:
Shyvana deals 25 / 40 / 55 / 70 / 85 (+20% of bonus attack damage) magic damage per second to nearby enemies and moves 30 / 35 / 40 / 45 / 50 % faster for 3 seconds. Shyvana's Movement Speed bonus is reduced over time.
Dragon Form: Burnout scorches the earth, continuing to damage enemies that stand on it.
Cooldown 12 seconds
Explanation: This is the best ability in my opinion. My personal play is very aggressive, and this ability helps me be aggressive and helps me chase people that are close to dead. You cannot run from Shyvana while Burnout is on.
E Flame Breath:
Shyvana unleashes a fireball that deals 80 / 125 / 170 / 215 / 260 (+60% of ability power) magic damage and burns 15% of their armor for 4 seconds.
Dragon Form: Flame Breath engulfs all units in a cone in front of her.
Cooldown 12/11/10/9/8 seconds
Explanation: I don't personally use this ability much in human form, but in dragon form this ability is great for farming and dealing a lot of damage to an area of enemies.
R Dragon's Descent:
Active: Shyvana transforms into a dragon and takes flight to a target location. Enemies along her path take 200 / 300 / 400 (+70% of ability power) magic damage and are knocked toward her target location.
Passive: Shyvana reinforces her scales, increasing her Armor and Magic Resist by 15/20/25. Defensive bonuses are doubled in Dragon Form.
Cost 6 fury a second and max fury to activate
Explanation: Hey. There isn't much to say. Your a Dragon. No but in all seriousness, this makes Shyvana a great initiator into teamfights. First off, she deals damage with her ult. Second off, her passive armor becomes DOUBLED. This is great. This is why I am king of diving turrets... >:)

The summoner spells I feel are best to use on Shyvana:
Ignite
Why: I like to tower dive a lot, but I try to avoid as much damage as possible. What I will do, is Dragon's Descent onto them under their tower, deal a ton of damage until they are low, then Ignite and run. I usually get the kill, and avoid being kited/receiving more damage.
Exhaust
Why: I love people who think they can just run from Shyvana, because she has no CC. Well here's my CC, Exhaust. They come up, deal a bunch of damage, and expect to run away. I deal some damage back, and then exhaust them when they run. Free kill. That's it. Even if they Flash out, I might as well continue chasing and just dive them.
Other Options:
Flash
Why: I only grab Flash if I think I will need it, for instance vs high cc champs so I can Flash out of the CC. For example Alistar, who is painful when it comes to CC.
Flash Is really the only other summoner spell I would throw on Shyvana

The runes I use are semi-standard AD Runes. I have been using the Greater Mark of Attack Damage, Greater Seal of Armor, Greater Glyph of Scaling Magic Resist, Greater Quintessence of Attack Damage. I am going to go ahead and explain why I get each rune.
Greater Mark of Strength:
Why: In 3v3's, you don't need as much tankiness. For instance, in a 5v5 with Shyvana you would usually have tankier more sustainable runes. In 3's, since you don't need as much of a tank, more of a offtank initiator, I get attack damage. The reason I like the flat attack damage is the early harass. You will have a much stronger early game and possibility to get kills with the increase of attack damage.
Greater Seal of Resilience:
Why: This allows me to not be forced to build as much armor. If I am having a bad game with Shyvana I will usually buy armor/Magic resist (whatever fits the need) so I have more survivability and more likely a chance to stay alive and clean up kills. I usually have good games as Shyvana and do not have to worry about it. This rune helps me get the right amount of early armor to survive vs an AD or someone building early AD.
Greater Glyph of Shielding:
Why: This rune is commonly used because of the increase of burst damage AP Carries. A lot of carries, once they hit level six will burst you down fairly easy. For instance, LeBlanc. She has great high damage burst at level 6. This rune gives you the M.R. per level to help you survive bursts of damage such as that.
Greater Quintessence of Strength:
Why: The reason I get this is basically the same reason for why I get the Greater Mark's of Strength . I enjoy the early damage. It helps me harass, and get early kills.

Wriggle's Lantern
Wriggle's Lantern gives you two great passives. The ability to have a free ward at any time so you don't have to facecheck something suspicious, and the percentage chance of hitting a creep/minion with increased damage. The free ward is great, and the creep damage is good for farming/jungling. Other then the passives, Wriggle's Lantern gives you a little bit of armor and life steal for sustainability and survivability.
Mercury's Treads
What is there not to like? Even if you are going against an AD heavy team, Mercury's Treads have the passive that can save your life. Increased tenacity is one of the best things you can ever get in my opinion. Helps with CC, and if they do have a semi-magic heavy team, that's a plus too.
Frozen Mallet
Frozen Mallet gives you so many things to like. Extra attack damage, extra health, extra tankiness. Oh and the passive. What's that thing Ryan loves to do? Chase. What does a Frozen Mallet allow you to do? Chase hard. The passive allows you to slow the target after hits, this is critical. This is another reason I dive. People cannot kite you as well if your slowing them with every hit.
Wit's End
What offtank doesn't get a Wit's End? This item gives you increased attack speed and magic resist. The passive is nice too. That extra 42 magic damage does come in handy.
Tiamat
How to describe the Tiamat on Shyvana... A lot of people question this item on Shyvana. Don't question it. The splash damage, when she is in dragon form, is incredible. Try it before you say it's not a good item.
Guardian Angel
Tanky? Check
Good damage? Check
Survivability? Check
Sustain? Check
Can you die? Not with Guardian Angel. So now you are tanky, and hurting the enemy team bad. You initiate a team fight, and they think they focused you out of the fight. Little do they know, you come back to life and eat their face.

Jungling in twisted treeline is very interesting. What I do, is play aggressively. I damage my opponents, and push them back to their turret. Every time my lane is pushed, I go into the jungle and kill some creeps. When I am not in the jungle, I go gank top lane and leave my laning partner on bottom. These are the two ideal things you want to do when your lane is pushed.

As the offtank damage dealer/initiator, your job is to initiate. You need to be the first one in the fights, and deal some damage. The ideal way to initiate is to Dragon's Descent onto their whole enemy team after some friendly harass. Then you should Burnout and immediately begin using Twin Bite to eat people's health away. Usually Flame Breath is a good idea to use after getting to the enemy team, because they will usually be grouped up. Always remember you can Dragon's Descent through/over walls for initiations/ganks also. Make sure you have proper initiation and gameplay, and the build will do you wonders.

Like I mentioned previously, this is my first guide. If you have thoughts opposing the guide, or didn't like it for some reason, please don't downvote it. Just tell me your thoughts and I will update my guide, and hopefully get an upvote ^^. Remember this is for 3v3's on Twisted Treeline. I really appreciate you reading the guide, thank you for your time.
Blakkout69