This is a Quick Guide but i will be Thoreau.

Given your looking up this guide, you probably dont know anything about this champion. As such we are going to start off with the basics of how to play poppy, and what she does as a role of the team.

Poppy is a Heavy hitting assassin type, best played as a sniper. meant for picking off people that are weak. attacking a pack is close enough to assisted suicide in most cases, so stay away from them unless you have your ult up. sometime you can land a kill or help a team mate out of a sticky situation, but it takes some tactical work to avoid your own demise.

When building Poppy, in my own experience its best to build a mix of easily picked up AP. which is why you will see so many items involving the Amplifying Tome in there construction.

VALIANT FIGHTER- Any damage that is dealt to poppy that exceeds 10% of her current health is reduced by 50%. this does not reduce damage from turrets. you will find this is a strong counter to people playing Veigar. The passive basically allows you to build AP and not worry about him popping an ult and 2 shotting you.

DEVASTATING BLOW- Poppy Crushes her opponent, Dealing attack damage Plus a flat amount and 8% of her target's max Health as bonus Damage. This ability does scale with ability power as well as attack damage. its important to note, devastating blow Does deal nearly 10% damage as base damage, not including scaling from armor pen and gear, this ability however, will not be your First talent to upgrade.

PARAGON OF DEMACIA- Upon being Hit or attacking, Poppy's armor and damage are increased for 5 seconds, scaling to 10 stacks at a time. when activated, this ability automatically stacks to 10 and increases her movement speed for 5 seconds. While this may seem like a sweet treat, the way it builds up is slow and not worth the effort until late game. Still, it is important to get the rank 1 on lvl 3 as you will be using this as an escape mechanic pretty well all game.

HEROIC CHARGE- Poppy Charges at an enemy and carries them further. The initial impact deals a small amount of damage, and if they collide with terrain, her target will take a high amount of damage and be stunned. This is your bread and butter. keep in mind the damage bonus from AP is Greatly superior when colliding with terrain. This is your ability to master, you almost never want to use this unless pushing the target into a wall.

DIPLOMATIC IMMUNITY- if you haven't read this ability by now i will fill you in. it allows you to target 1 enemy and deal 20% additional damage to said target. in addition, you are immune to all damage coming from ANYTHING other then your chosen target. with that said, HOLY MOLY ITS A PONY!

Poppy accedes in Player Sniping. by that, i mean harassing without saying sorry, actually its more like saying "here's a towel, clean yourself up". Poppy is relentless. in such, Poppy Should be played VERY offensively, at least after she gets Soulstealer anyway.

Best Paired with Xin, Singed or Blitz. she is outstanding with a champion that can position her target for her. if you find yourself without any of these, try experimenting with flash a bit for fast positioning and with her "W" Paragon Of Demasia.

Your Rotation is a 1234 repeat method similar to Blitz(with different key strokes). "R"E"Q"W". Personally, i find the damage buff from W to be underwhelming at best, which is why i use it for the 20% speed boost it gives to ether get away, or finish a kill if the rotation leaves them with something.

Touching on the heroic Charge for a quick moment, id like to give some tips in how to help your team out and avoid letting a kill get away. NEVER heroic charge a target unless you will push them away from there turret, or into a wall. your heroic charge has an Over push or carry if you will, that can actually work out in there favor. It will be pushing them closer to there tower and giving them a better chance of survival.

A Quick thought on turret diving. if your unfamiliar with this, its following up on an attack after your target has retreated under a tower. while turret diving is dangerous in most cases, Poppy is able to pull it off if only for a couple seconds to finish off a weak target. With that said, dont try this on someone at 80%+ unless your feeling Pretty confident and got the Gear to pull it off.

To Properly execute a turret dive with Multiple people, be sure to enter first, as your ult will soak up the dmg your partners could be taking. While Entering into range, Position yourself so your "E" heroic Charge pushes them into a wall, This Maximizes your Damage and stuns the target for a couple seconds. The button Combo your looking for will be "R click target, E Click target, Q,W. If you are running Ignite, toss that out as well if needed. you will then run to the perimeter of the turrets range, but not outside of its range until after your Ult is down. this increases the chance your partners can get out as well unscathed.
Remember, you can push your targets into the turret itself as it does count as Terrain.

The Build i introduce in this guide is one i personally use, however in most 3s matches i cant build Deathfire or Hextech, Which you will come to understand is actually a good thing (considering winning is Incredibly fast).

Start With a Simple Amplifying Tome and a Health pot. Ganking at the beginning for ether 3s or 5s is recommended but by no means necessary.

as you progress to lvl 6 head back and pick up Ninja tabi, The Dodge chance will save you more times then you think. your next item will be the Mejai's Soulstealer. then a Sheen. by the time you get Sheen, you should have tried a couple times to find a kill here and there to stack the soulstealer up some. After your Sheen, you will be building the Phage and the rest of Trinity Force. Trin. is an important staple, as the speed boost and slow are devastating when singling out targets. Build yourself a Sheen again and then the Lich Bane. Lich bane is another important staple in this as the burst damage it allows is out of control.

you will find a DeathFire and Hextech. Both can be swapped for w/e you feel is necessary to your situation, they are just simple suggestions more then anything. deathfire is for finishing blows if your rotation is failing to kill a target or Ignite is on cool down. Hextech is for survival for late game. getting jumped can be scary, but can easily be turned around with a ult pop and E->Q. also, hextech has another ability which with deathfire can fill the gap between E and Q's Cool downs and minimize downtime in damage.

other suggestions would include the rabadon's deathcap X2, which could nullify the need for both hextech and deathfire, but can reduce your survival tools down to just the ult and passive. it will also be costing about 1000 gold more. for the combo.

items you can consider on your own would be The Zhonya's hourglass and Guinsoo's Rageblade.

You will find that with a team of people more offensive you will get a better score more often then not. with that said, farming minions is only really ganna happen from lvl 1-6 and between enemy spawns. farming kills will eventually get slow however, so switch to minion slaying to force enemies out of a lane or baiting them into yours.

i will be constructing a guide on how to build AD as poppy as well as a tanking guide to poppy.

as crazy as it sounds poppy can tank pretty damn well with the proper gear and play style, but i will be back with those another time.

have fun and Good luck summoners.