Warwick is one of the easier top lane champions to play. This is due to his natural sustain from his passive, his Q, and the utility provided by his E ability and his ultimate. I recommend Warwick for any summoner looking to improve on their team play skills and over all communication.
Once your lane phase has ended, whether you've pushed your enemies tower or lost yours, Warwick becomes a monstrous roamer. DO NOT get kill hungry when you roam. When roaming on Warwick think with the mindset of a jungle champ- If you can get the kill in mid that's fine, but it would be better to feed it to the 1/1 mid who hasn't been doing so well against their counter part. Remember, assist gold is still gold.

Warwick's spells revolve around two concepts; Sustaining yourself and positioning.
Let's start with sustain. Warwick's passiveEternal thirst deals magic damage on hit stacking up to three times and heals Warwick for 100% of that damage. This gives you a slight edge over the champions that start with a Doran's blade as you'll out heal their sustain. His Q Hungering strike, improves upon that. His Q hits for the greater value between the damage labeled on the tooltip and a percentage of the enemy champ's health, and heals Warwick for 80% of the damage dealt. For an example, if at rank two of your Q your enemy has 2K health it will hit them for 200 damage(10% health) instead of the 125. It will also heal you MORE if the target you hit takes the percentage damage. Lastly on his Q it has a very small amount of range to it, maybe a minion's distance between champs and be used to smack a champion as they try yo enter melee range.

Positioning!Blood scent it the reason I take the 3 points of increased movement speed masteries and mobility boots. The speed between the two of them gives you insane map control when you communicate well with your team and work with your jungle. You will want it on constantly in your lane. If your enemy gets low and pops it, you'll be able to flee should them taking damage been an attempt to bait you for their jungle. Speaking of the jungle, when in any jungle, toggle it on and off to search for players. If a player is low enough to trigger Bloodscent they will get a debuff notifying them of this. You toggle it on and off so you don't give yourself away during ganks. Conversely, you can keep it up as a bluff near objectives such as Dragon or Baron. If the enemy believes you are near a low health player at such an objective they will be more cautious and may simply ward it as opposed to grabbing it. Use of fear tactics to zone in on enemy players, get around the map, draw some aggro off a team mate, back door, or flee is absolutely crucial.

Warwick's ultimate is his most useful move. As the tool tip states, the target is suppressed, Warwick deals more damage and gets increased life steal during this, and applies his passive and on hit effects.
Of course you can use it to engage, or to chase, or even to interrupt recalls and ultimates of some champions. All of those are fine options but it is best used with a dash of common sense. That being said, don't use it if you know you're going to be caught out during or after your suppress. Always use it on targets that will ruin team fights. If the Adc is pumping out tons of damage then you need to stop and think about it. Is it really Draven that's ruining our team fights? Or is it Zyra's stranglethorns keeping us still? The last bit I'm going to say on his ulti is more important to laning phase but can be used whenever really. You can use summoner spells while you're ulting! This means you can pop ignite on targets while you're Pew pewing them. Make use of that, you'll love it.

Starting from level 1-3 there are two possible choices.

Harassment start L1Q, L2W, L3E then max Q and fill as needed

Farming start L1W, L2Q, L3E then max Q and fill as needed.

Above I've listed two sequences to grab your abilities during the first three levels. In this paragraph we'll discuss how to use both of them to farm efficiently. The harassment start starts with your Q and will have you last hitting, using your Q to poke an enemy champ when they go for a minion to deny them their farm or to defend if they poke you. The Farm start has you start with your W. Your W will increase your attack speed for a few seconds and as such will allow you to last hit minions quicker. Taking your W first also allows you Greater Lane Control over your opponent. Your W also increases nearby ally attack speed by half of what you get. This includes minions. Ideally you want to have more of their minions up than yours while farming, and to let them push. Using W to increase attack speed of your minions at the right times will end up with you having more caster minions then the enemy(This occurs usally if you use W defensively to out farm them and deny their farm when they've pushed you to turret) at a time which will in turn deny them increase your farm and deny them theirs.

You can start with any of the Doran's items, it all depends on your play style so here's a brief overview of them.
D-blade- gives your more damage & susstaing for last hitting- better suited to aggressive early game.
D-shield better suited for defensive play & absorbing damage against a heavy hitter (Buy this if you feel iffy about taking mobility boots over ninja tabi).
D-ring is what you will want to take to farm early with. IMO it provides the most use as the mp5 is useful up until late game. Warwick's Q scaled Straight from AP as well, keep this in mind.

On your first back you will go at 800-900 gold & want to start your boots and grab either a long sword or a dagger.
If you grabbed a long sword first, on your second back finish it to a vamp scepter and grab the dagger. If you grabbed a dagger first finish a Zeal and then start the vamp scepter.
After vamp scepter/zeal start your phage then get back to farming.
Finish your trinity force.
Once Tri is finished farm up for your mobility boots and buy them asap as well as wards! (By the time you have your tri if you haven't won lane yet or are just keeping it a farm lane they will try to shut you down hard)
after tri start your Nashor's tooth by building the codex first over stinger.
If while building nashor's you want to make your vamp scepter into a bilgewater cutlass that's fine. You could even build blade of the ruined king before Nashor's tooth if you wanted to.
After Triforce and your Nashor's tooth you will want to rush that Spirit visage ASAP. Once you have Spirit Visage & Nashor's your CDR will be maxed and your W will be off cooldown by the time it's duration ends which is very nice as with a Tri force & Nashor's you will have at least 2.00 attack speed with W popped. The maxed CDR will also have your ulti set to a 42 second cooldown.

Final options!!! For your last item slot I usually recommend a Warmogs' armor. Following this build the Warmog's will put you at around 3k health. The other option is a Black cleaver. Both are fairly expensive but decent finishers for most teams. If the enemy team is Really AP heavy I would advise against Wit's end because of how high your attack speed is. IF they are AP heavy, finish your last item slot with a Spirit Visage or a Maw of Malmortius.

As I mentioned in the intro Warwick is a great champion to practice team work with due to his utility. Communicate with everyone on the team if possible, but make friends with your jungle. Work well with them and you will have a great time. Always ping your MIAS!If you notice them go into the top jungle, or yours, or to gank your mid, ping the MIA and actually mention which direction you saw them coming from. Not everyone will read it, so follow up with some danger pings in the direction of the route you see them going. If your jungle doesn't notice your mid will appreciate the heads up and be careful.
Wards: Not just for supports! I do not mention it in the item build at all, hoping that most people are already in the good habit of warding. If you're not, or you're under the illusion that it's a jungle's responsibility to ward your top it's not. Every time you back to buy an item, following this guide, or another guide for any champ. Use your excess gold for wards! Bought something and have 200G? Your next item costs 400G but you won't be able to B for the next 10 minutes? don't let it go to waste pick up wards :P You will want to keep your river bush, and their Tri bush warded. This is for your sake so you can see the enemy jungle coming up and back out as needed. It is also for the sake of your jungle- they can't gank if your enemy is warding so Always ward and counter ward. On top of that if you see them ward but have no wards to counter ward, let your team know. Ping the bush, or spot in river and say " ______ is warded". Last bit on my ward rant here! If you can afford a third ward, then use it to watch the enemy's red buff or your blue buff. If you have it warded you can gank/steal theirs and defend yours.

This has been my first guide so any feedback is appreciated as are questions about item choices or what ever. I put more emphasis on trying to explain a few tricks for team play because as I've said a few times Warwick is a fairly easy champion to play without a guide or reading any of this, but he's so much stronger when you communicate with your team.