Hey this is Phallen with my first guide introducing Jarvan IV. So far as my experience is, he is a very strong hero and i play him as a dps hero but with some health to withstand some dmg. Im sorry if im lacking the icons and whatnot that better guides use, but i feel like the information is the most important part of guides.

Alright so the runes i chose are ones i use, mostly because they just work for me. I get the armor penetration because lets face it, hes AD which means armor is not Jarvan's friend. I get health quintessences and health per level seals because they keep him alive and considering his ultimate traps you with someone else, being alive is a good thing. Finally cooldown reduction runes, its kind of a toss up for these, but i really like being able to throw flags at people...call me crazy :P.

Ok shortest section without a doubt. I appreciate ghost's ability to catch somebody at all parts in the game. I also love exhaust. I feel like exhaust is a must considering when your trapped with somebody with your ult who MIGHT deal more dmg (idk how they could) but have lower health exhaust reduces their dmg and gives you a chance to kill him or gives time for your teamtes to come to your rescue.
Other Options
Flash-a fun, handy little initiator, but the escaping wont always be necessary as jarvan.
Cleanse-uhm, i dont usually use Cleanse myself, but hey who doesnt like a "get out of jail free" ability?
Teleport-Useful for defending, Useful for ganking, would probably get it if exhaust wasnt so freaking spectacular.
Ignite- maybe, if you really have issues catching somebody, which you dont...so there :D
Revive- ok..well i find this to be underestimated with some heroes, a revive on a team full of solid burst heroes with not-so-good survivability, revive could be used to stop a push or keep one going if you get picked off..but we are trying to prevent that with Jarvan :).
Fortify- useful, best left for tanks IMO.
Clairvoyance- why needed when you already have a bush searcher ability?
Rally- maybe if you use it a LOT.

Not-so-good Options
Smite- you dont jungle with this build or lack farming abilities with jarvan.
Heal-no, i dont ever use heal, i know some might but who needs it if you have starks and over 2.0 attack speed.
Clarity- eh, not really needed it because spamming isnt really needed.

I go 22/7/1 because of my summoner spells for the 1 in ghost. He needs the crit because when Jarvan is farmed and can crit on every other swing crit dmg really helps. Attack speed...yadda yadda...it seems to be pretty obvious choice of masteries for me.

Alright so items are the most important part. I start with boots because early game Jarvan can dish out a TON of dmg and firstblood is capable almost anygame. EDIT: Boots of Swiftness is very viable as well, i dont always get it, BUT it can help get Frozen mallet hits off, and Beserker Greaves could work as well Sapphire Crystal for early mana. Frozen mallet is a good item first because of the slow and health. The health keeps you alive and the slow makes early kills easy, combined with Demacian Standard he is impossible to escape without help. Catalyst helps with mana and health early on. Phantom dancer makes it even easier to chase and deal more dmg faster with the crit and attack speed. Stark's helps with lifesteal being useful..more attackspeed MORE reduced armor. More than likely the game will be over before the starks is obtained, but if it keeps getting dragged out. Banshees veil helps a TON against heroes that have a lot of burst, the catalyst is already there so its just easy mana and survivability. Black cleaver removes armor which referring to what i said earlier, no armor is Jarvan's friend ^_^. It has a ton of dmg and this just ices off the cake when it comes to dishing out dmg very quickly.

Recap: What have we learned so far?
Attack speed is a necessity
Reducing other's armor=win
A little extra health never hurt anyone :).

EDIT: Other Options
it seems i this earlier, i appreciate the comments suggesting some ideas
For Jarvan getting blue buff is very viable to avoid mana issues, BUT if you love harassing that squishy little sivir in the side lane, Getting tear of the goddess early on and then turning it into a Manamune maybe after the Zeal would probably give enough chance to get at least an extra 500 mana at the minimum!. Most likely the infinity edge wont be obtained because games end quickly with solid teamates, so this could just be inserted after the zeal and just remove infinity
Optional Items
If the other team has a ton of physical dps, Thornmail OR Randuin's really helps
If they have a lot of magic, like i said earlier Banshees is my favorite, but Aegis of the Legion can always help because hey, auras help teams fellas. Nuff Said :P
Last, jarvan can be turned into a tank if really needed to, i dont prefer it but hey, might as well throw this in there. I like banshees, randuins, aegis, sunfire, warmogs, and maybe force of nature, just throwing that out there..thats not my build tho :)

EDIT: Being Harassed
From a helpful hint from Steelek, he mentioned that Jarvan could have issues if being harassed and having no lifesteal. I changed my original build to make starks before black cleaver. Helpful comments like this will continue to make the guide better. :D

Skills ok...really important but really simple. Getting one point of Dragon Strike, this reduces armor the same at all levels and does some decent dmg scaling with attack dmg.
Demacian Standard is the most importantly placed ability in Jarvan's arsenal. If anyone can read, he throws a flag down and does an AoE magic dmg to whoever is within the range of it. It also doubles the buffs that the passive already gives Jarvan to him and ALL of his teamates near it.
Important tips for Demacian Standard

Well one is the scouting uses of it. It gives vision into bushes so throwing over a wall into a bush to stop an unexpecting ganker off-guard could be the difference between life and death for Jarvan
Also, the most underestimated or underused use of it unfortunately, is the knock up affect of it. When the flag is thrown, it creates a target for Dragon Strike which would pull him to the flag. This combo knocks up anyone in his path and also a minature range behind the flag as well, so if u throw the flag ahead of the target but the target is fast, you may be able to knock him up still.
Using the attack speed buff of the flag knocks down towers really fast, making pushing a breeze making Jarvan one heck of a champion.

Golden Aegis is a very useful spell for tower-diving or when multiple targets are near Jarvan.
It creates a shield around him for a base amount PLUS another amount for each champion nearby in the radius of the ability. This creates a very handy shield when being chased OR while tower diving to survive another hit or two from the tower's "laser guided affection"
It also slows down all of these enemy champions hit as well...yet again...do i really need to repeat? TOWER-DIVING!!
This Demacian steam-roller isnt complete without his ultimate. Basically in a nutshell...he challanges someone to an "ultimate" showdown (ignore the pun) This blocks off everyone outside the area affected by his ultimate, and can be despawned if needed by hitting "R" again.
Uses of ultimate

Can be used to separate enemy champions and can beat up another team's rhythm.
Second, one of the best ganking spells in the game. Say a friend is getting beat up by a ranged little jerk..lets say twisted fate. Your friend runs up and auto attacks him melee or if ranged this little step isnt needed. Jarvan runs in, flag, dragon strike, and then when that card-stacking little jerk finally hits the dirt an ultimate is amazing here. It makes it a 2v1 with no help from his teamates until the walls finally fall down. By that point hes gone.
If you manage to be stuck in your own ult, you can throw a flag out of the arena and dragon strike to it, this leaves the enemies stuck in your walls of fun while you get away with a smile on your face.
If the same scenario happens but near a tower, why waste mana and dragon strike out when you could just hit R and then run away to save the mana.

SOOO keep in mind, combos are fun :D

OK so besides what was stating already. Here are other tips.
Ok so flag-dragon strike can escape a lot of holds if not all of them...ive ticked off many of Amumu's and Warwicks by just throwing the flag and timing dragon strike just right to knock them up to stop channeling spells like Warwick ult or escaping Amumu's ultimate like Harry Houdini.
Ulting within teammates can make one enemy a very unhappy camper when surrounded by 4 of your allies hitting him for free.
The shield can be one amazing way to get targeted, but still survive, and the slow well what more can someone ask for?
Hitting all of the enemy champions before focusing one may be the most viable way to deal dmg because of his passive, which says he deals 8% of current life to targets every couple of seconds. AKA hit each target, does 8% of each enemy's full health right off the bat, followed by focusing makes enemies LESS likely to turn around and try to save their friend "SORRY cant risk dyinging!". As much as i hate to say it, we all tend to care more about our scores than our wins, so this helps make your team do BETTER because in the long run more targets are brought down with fewer casualties on Jarvan's Side.

Alright. So like i said Exhaust Ghost are my favorite summoner spells.
Attack Speed and Armor Reduction make Jarvan one scary man.
Use flags frequently to bring down towers, scout, kill champions, running away, knock ups, escaping ults, chasing enemies...etc.
Ult wisely, one Jarvan does not want to be surrounded by 5 enemies frequently.
Assist teammates at all times! A well played Jarvan is a formidable force.

Good Luck Summoners! Take this one brutal Demacian and dominate the league!