Jarvan IV is one of the best tanks in the game, I always play him as tank, his crowd control can save lifes, get kills, and carry your team.

Jarvan is very good as jungler (off tank), but I still prefer going lane with him.
You can see here the SaintVicious's Jarvan jungler.

In lane you have 2 choices:

Go solo top. He's not the best solo laner, he can be easily owned by Singed, Akali, Cho'Gath (the best solo top laner), Nidalee, and other champions that can Harass or Heal.

Go bot and support your ad ranged. You won't be farmed, that's the only problem, but going bot is one of the best things to your jungler, the gank works almost all the time.

I prefer the second one =D

As runes I choosed

Mark: Armor Penetration - Give you more power
Seals: Armor per level - People say... WHATAF**K. I use armor per level because Jarvan already have his passive of Demacian Standard, and this runes will give to Jarvan the best mid/late game.
Glyphs: Magic Resist per level - you don't need flat when you are using quintence flat
Quintecense: Magic Resist flat - will give you a good MR in early game, and glyphs will give you a better mid/late game.


With this runes your mid game rules =D

But if you don't have this seals and quint you can change. All the options are good:
Seals:

Flat Armor
Dodge


Quintessences:

Flat Health
Flat Health regen/5
Dodge

My Jarvan is TANK... so 0/21/9 is the best choice.

Well...
Start with Regrowth Pendant + 1 Health Potion
At your first back you take Boots + philosofer's stone (715 gold)
At your second back you take heart of gold + Mercury Boots if possible, if not, do null-magic mantle. (1675 gold)
Than if the game is sooo muchhh easyyy your start building Warmog's, if its not, Start building Frozen Mallet, that will give your team a lot of kills with this permanently slow.
If they get champions with good normal attack, like Master Yi, Ashe, Caitlyn, Miss Fortune, Vayne, and they are fed, you build Thornmail asap.
Or you can do Randuin's... that's a very good choice.
If they get a nuker and it get fed, do Force of Nature asap.
In very end if its hard do: Guardian Angel and yours Warmog's to tank a little more.
If its easy do or Warmog's + Atma's to have more damage.

The best choice is R>E>Q>W
E - gona give you more armor and attack speed, so you gona be good tank, and help your team to push turrets at mid game.

Flash + Ignite is the best option for me, I have a massive damage with combo + ignite specially at mid game.

Flash + Exhaust could be so good to, depends of what you prefer.

Ghost is not that good to him. I use flash so I can combo flash + ultimate and trap the enemy =D

Jarvan can farm just with normal attack at early game, because his mana is one of the biggest problems of Jarvan.
You need keep mana to be ready for your jungle in his ganks.

YOU are the TANK.
YOU start TEAMFIGHTS
YOU choose the right time to engage.

So, You gonna carry your team.
Well, the right time to engage in a teamfight I can't tell you, depend how is going the game.
But try to trap their carry and most strong guy with ultimate, so they'll have no chance to run, and your carrys would kill them.
Ulti can save lifes too, so you need to use that in the best moment, it can decide teamfights, and decide games.