Jarvan is the newly released hero as of 3/1/11

Pros:
Naturally Attackspeed + armour
Can do a nice amount of damage even built tanky
Knock up + wall trap = great CC
Has a semi escape mech
Easy to last hit with

Cons:
Easily focused because hes melee
Flash is his worst enemy because it counters his ultimate
needs to farm up to be good and do any damage

Marks: Obviously armour pen because its the only thing i feel like that works. Everything else such as attack speed, or anything else isnt as important as pure early armour pen

Seals: Now this is optional, imo i feel jarvan lacks mana in the game untill he grabs a banshees so the seals help to give him a decent amount of mana supply. You can change it to armour yellows or hp/lvl yellows but its entirely up to you

Glyphs: Again this is optional, magic resis per level would be fine but not CDR, you get enough CDR with ghostblade,CDR boots and randuins

Quints: HP Quints just for the early game survivability, you can change this with armour pen quints.

21 in the def tree because offense is useless
9 in utlility because jarvan isnt a magic pen champ

Cloth armour + 5 hp pots. Why? Early game survivability and it should help you farm up more

Next recall: Buy Heart of gold and boots, If you cant afford heart of gold early on then just get boots.

Now that you have a a heart of gold for an extra amount of gold its time to build up some power.

Ghostblade : Provides CDR, Active AS + MS, armour pen. Things that alot of AD carries need

Banshees: Rush this early on if your having trouble surviving the game, or if they have alot of CC.

BT: Ghostblade gives you a decent amount of power but a bloodthirster just makes jarvan insane in his dps output. Provided with lifesteal jarvans ult + E Q combo is deadly.

Last item is usually a randuins for me, but you can replace the heart of gold if you wish. Jarvan gets a decent amount of armour from his passive on his E so you can skip it, but a randuins + ult combo is pretty darn good.

Max Q first because of the early armour reduction and its poking power in laning phase.
Get 1 into both W and E before level 3 so you can do a full combo if needed.
E is your next priority because of its passive benefits. W is last because your shield is decent enough at level 1 and it gets better if there are more enemys around you.

Laning Phase: if your having trouble getting last hits, just use your Q to last hit if you can do it without getting harassed. Jarvan is a good farmer naturally with his passive and his Q makes it more easier since its ranged

Teamfight: usually you should try to ultimate on the carry or if you have another AoE champion use it on champions crowded together. Try to pay attention to see if they have flash or any other escape mechs.

Ghost to catch up to people and ultimate. Can also use it to get away from bad situations

Ignite/Exhaust: Up to you, i usually grab ignite because jarvan is a carry and exhaust is usually something i let the tanks get.

Other spells i feel dont really cut it.
Clarity- mana issues for jarvan, but mana regen seals and conserving mana means you dont need this at all.
Heal - with a BT you dont even need to look at it
Flash: This is kinda preferable, i dont like it too much on jarvan because jarvan needs MS to catch up and rape faces. Flash is just preferable by summoners
Teleport: if you want more lane coverage feel free to take it
Cleanse: This is a maybe. you can take it but like i said its up to summoners if they want to take it or not.
Revive/Rally/Clarivoyance/Fortify: No Just No

Jarvan : DEM-A-CIAAAAA
R-Q-E-W And Pew Pew dead