DEMAAAAAAAACIIIAAAAAAAAAA - he cries, when he jumps to the enemy to kill him. Enemy can't escape and soon will be dead. That was another fight Jarvan had won and he did win after this fight too, and for many times.

I think that Jarvan IV is one of the best champions in the game. He has one of the best ultimates in the game and good attacking/ganking/escaping abilities. For example he ults and then he flashes out or does his E and Q combo to get out of certain death. He can jump over walls with this combo and if Jarvan IV is Dragon Striking to his Demacian Standard, the enemies in the path are knocked up. That is a very good combo, when he does his Golden Aegis too. It's like some damage, knock up and slow at same time. Enemies will always fear Jarvan IV.

PROS: Very good team player and can solo too
Good survivability
Good passive and abilities
Combo from E and Q
Good harassing possibilities
Most beautiful ult Cataclysm in the game
Can also be played as a tank or as an AD-offtank
Suitable for all lanes

CONS: Can be easily killed when his abilities are on CD-s
Very mana-hungry early game
Ult can work against him and his team.

I like playing Jarvan since he came out. He can nicely work in cooperation with many champions, for example Nocturne or Blitzcrank. He can be easily played as a jungler. This is a laning guide, not jungling guide. At starting, Jarvan has a good amount of health, and he is strong at making damage, but his mana is low. When he reaches lvl 2, Jarvan starts to be strong with his combo (but runs out of mana quickly, unless you don't spam your spells) . It is like a shock weapon to enemies and it does alot of damage. When I reach lvl 3, I will upgrade my Dragon Strike because of it's solid amount of damage. After lvl 4 I upgrade my Golden Aegis because of it's slow and shield (which is not that good, but may save you sometimes). I upgrade my ultimate at lvls 6, 11 and 16. First I max my Q, secondly my E and thirdly my W.

Quints: I take Greater Quintessence of Health because then I have increased survivability. Jarvan mostly lives on his health. Why I didn't take AD Quints? Because Jarvan IV already has a lot of damage from his spells and passive and it's enough to bring enemy down or to farm.
Marks: I take Greater Mark of Armor Penetration because then I have even more damage output with my armor penetration. These are just good runes.
Seals: I take Greater Seal of Armor because i want more defence against other top-laners (almost always AD). It gives me great boost, because enemies need to spend some gold on armor pen. when i have these runes.
Glyphs: I take Greater Glyph of Magic Resist because I need good counter against AP-casters too. It gives me a good advantage over enemy AP-heavy champions because I can counter their damage better then.

My masteries are 18-0-12. It contains both attack strenght and survivability.
My offensive tree contains bonuses for AD, Attack Speed, Armor Pen and more damage.
My defensive tree contains HP, Armor and Magic Resist. Nothing to explain there. I just need those things to survive better.

In early-game I last hit minions with my physical attacks, but when my Q is getting stronger, then i can farm with my Q too. Sometimes I take out full minion waves with my Q. Dont forget to LAST HIT minions with your basic attacks, Jarvan IV makes it even easier because of Martial Cadence
Early-game harassing is with Q and E, but not with combo. You do combo when you want to take out that enemy. Sometimes I get kills when I am level 2 to level 4 easily. When it happens, I can get kills every time I want because I am alredy getting fed.
Killing spells: E, Q, W, E, Q.
After lvl 6: E, Q, R, W, E, Q.
Both times enemy will be dead or seriously injured, that you can kill them with 1 physical attack.

My spells are Flash and Ignite, because I almost always play with these spells. These are very good spells for Jarvan for killing and escaping.
About another spells:
Exhaust: I could take this too, but Jarvan already has built-in armor pen, slow and another good buffs. It is good though, because it prevents enemies from killing you because of the attack speed debuff.
Ghost: Nice movement speed buff, but I'd better take exhaust or flash.
Teleport: Very good spell to Jarvan IV, he can quickly change lanes and go to base and quickly back again. Very good spell to replace with something.
Clarity: At starting good, but pointless at end.
Heal: Same as Clarity
Clairvoyance: You already have your E
Cleanse: Ok, but no.
Smite: For laning this sucks, but for jungling it's good. This is not a jungle guide.

Martial Cadence (passive) - A very good passive, does a percent of enemy HP as a damage. Very good for harrassing enemies.
Dragon Strike (Q) - Good amount of dmg, nice passive at enemies and friendly range too. Gives a good boost in your damage and works awesome with your E
Golden Aegis (W) - Good shield, but doesn't block a lot of dmg. I take it because of slowing effect, but at lvl 5 the shield is good too. In teamfights it is ******* how useful. It gives bonus shield per nearby enemy.
Demacian Standard (E) - Bread and butter for Jarvan IV. Gives attack speed, armor and makes a nice amount of dmg. It is the second part of his Q and E combo. Good is this, that it gives AS and armor to all nearby allies and it works as a ward too that you can check bushes with it.
Cataclysm (R) - Most beautiful ultimate in game and it does solid amount of damage too. It can be a most useful ultimate in the game, but it can easily work against you and your team. You must have right timing to make arena or to collapse it. You can block enemies from escaping, but don't use it at enemies who has summoner spell flash or has built in blash or some kind of dash/jump, but with this build you doesn't have to fear that, your spells are doing great amount of damage already and you can follow them with your E and Q combo, that probably already kills them. If not, few auto attacks and enemy will be dead.

Fizz - Most annoying champion to play against with Jarvan IV. He can avoid your E-Q combo and ultimate (both damage and block). Also, Fizz can go quite tanky and deal alot of damage at the same time, which can end Jarvan IV easily.
Tryndamere - One of your worst nightmares. As you are a burst champion, when your spells are on cooldowns, he can beat you down without much effort. He can also heal all the time without the fear of losing mana (because he doesn't have it).
Shaco - Not as much as Tryndamere and Fizz, but can be annoying. If you can delay him from putting his Q to escape, you might kill him with your burst, but if he survives then he will escape.
Ahri - Not so much in top, but mostly in midlane, she is really annoying. She just moves around too much for you, especially after lvl 6. Also, it is hard to lock her down with your ultimate.

There are also champions, which can make your ulti work against you and your team, Fiddlesticks, Galio or even Nunu & Willump.

This is my first guide and I just can't put pictures or videos in it, you can comment or help me to make it better.
Don't downvote if there isn't any exact reason to do it.
Comment and always say if there is anything wrong in this guide. I will always upgrade and update it and I will answer your comments if you ask me to do it or if necessary or if I want to do it.