I've been playing League of Legends for a little over a year now and I've never really even been decent until recently when I picked up Pantheon. Now I'm far from the best Pantheon player but hey i get usually 10+ kills per game and out of probably 30 games with him over the last few weeks I've only ever gone negative once. This guide is similar in some ways to WorldsDeadliestBaker's guide off which i first started playing him so if you want a guide thats for higher tier play hit up This One :). This guide is how i play in solo-queued non-ranked games where the idea is have fun get kills and dont die.

Pros

Powerful early game (I get first blood probably 2/3 of the time)
High damage output
Good capacity to turret-dive for kills (with his passive)
CC-lacking physical dps carries fall before you (xin zhao, yi etc.)
Ult gives good map presence
Looks epic.

Cons

Squishy
Often focused in team fights
His E only works if aimed right
Cannot carry a team (well)

Esssentially being as though this guide is, as I said, for casual play; this playstyle is all about maximum for kills maximum fun :) again if you want a similar guide that's more team-minded hit up this one.

Mentality

This is a casual gameplay guide and as such there are a few pointers one must remember: 'when the going gets tough, patheon uses flash and ghost to flee' and 'any kill is Pantheon's kill' now of course I'm not advocating killstealing or screwing your team via ditching to save your own skin but those will definitely improve your K/D ratio... :). As I mentioned in Pros/Cons, Pantheon cannot solo-carry a team and if you decide to steal all the kills, which you can (and it's fun as hell) you will lose 2 times out of 3. It is better if you spend your time making it so your co-carry gets fed or at least is in a better state than the enemie's, this will ensure lots of wins. But as always, pugs are pugs (WoW reference lolz) and you will often be stuck with people who completely suck and go negative 3 then call you a nub for not saving them 5v1 and in these cases you will likely still have a positive K/D but you will lose because he cannot properly carry a team.
Protip: The reason we use is not for the lifesteal but rather the stacks and how they make it the highest AD item in the game, thus after dying/just aquiring the Bloodthirster it will help immensely if you kill a minion wave or 2.

Skill Combos

-> -> is your best friend, it can do insane damage at all levels (our armour-pen from and keep damage strong even against tanky-types). Whenever possible try to W before E because of the rather small cone of damage its all to easy to get out of, when you cannot W before E at least try to aim it in the enemies most likely route of escape (this will take practice and is never 100% certain anyways but after a few games you will get the hang of it).
Protip: When using , in the second stage of casting hit your and target the person in your ult whom you wish to stun because you will instantly jump to them once you land, this helps more than you might think.

Early Game

If at all possible try to lane with a character that has good 'hard cc' as i call it (stuns/roots) or 'soft cc' (slows, fears, silences). Having a competent lane partner combined with your and should get you a first blood more often than not. From then on continue to harass with , make sure you dont over-harass to the point of going OOM (a regrettably common mistake among panths). Use your whenever possible, it does lots of damage especially after your second doran's blade.

Midgame

Once you hit level 6 your job becomes stomping carries and supports into the floor. A decent idea of whats going on in the other lanes will secure you a ton of kills, That ashe is chasing your malz back to mid turret at half health? JUMP IN THERE. Up on top teemo and garen have a slight advantage over your mates and are pushing? BOOM DOUBLE KILL. Things to be cautious of are champions with either stuns, heals or lots of armor (or worse... all 3 like or . Panth hates them.) because these things can throw you into a drawn out fight which is not at all the specialty of Pantheon. Almost any CC is the bane of Pantheon, thus one must play intelligently and prey on the weak, you're scouring the map for glass-cannons, supports and that one low health warwick who managed to juke your team in the jungle.

Late Game

This is when it gets tricky to play Pantheon because everyone is sticking together and drawn out fights are expected so now one must adopt a new mentality: wait. As opposed to the "DEATH AND GLORY" style you play for the beginning parts of the game now one must play the Panth who quitely waits for a teamfight to begin and then ults in or runs in to the back of it. Late-game Panth ensures that stragglers never make it to team fights and that the weak/injured enemies cant escape justice. Also it is important to note that one should excersise their own best judgment on how the builds later items are prioritised, against a heavy caster team one might want a rather than a second .

Firstly to show you that I'm not TOTALLY bs'ing this guide... um... ya anyways here's my most recent matches! :)
So ya guys hope this guide helps ya play a better pantheon, have any suggestions or feedback hit me with a comment below, if ya wanna play a match sometime hit me up my summoner name is BenOfOlympus. Thanks all!