The reason I chose Greater Glyph of Shielding, Greater Mark of warding, Greater Seal of Resilience and Greater Quintessence of Desolation is because Warwick will get a lot of magic resist and armor.
Greater Quintessence of Desolation, I chose because it is often other players buy armor, so it's not a shame and buy them.
Overall, Warwick will have 32.7 + magic resist, + 12.62 armor, and 9.99 Armor Pen.

It would certainly be better with some other runes than Greater Seal of Resilience, but for me it has worked really well.

The reason I chose Doran's Ring is because Warwick will have MP5, AP, to Hungering Strike and 100 Hp, so there's mana almost always certain to use his spells wisely.

Now you will probably thinking, why Thornmail? Because Warwick will have 100 armor and 30% damage back on auto-attacks, If Warwick comes in against a Master Yi, or Tryndamere, 30% of their auto-attack comes right back in his mouth at them again.

Again, you will probably think, why Frozen Heart? 500 mana, more Hungering Strike, and 99 armor, 20% cooldown reduction, also provides more Hungering Strike.

More Hungering Strike more Hp, more Damage, More Fun;)

If Warwick playing against, 4 AD and 1 AP do not buy the Force of Nature, Buy The Bloodthirster instead.

If Warwick is playing 2 AD and 3 AP buy Force of Nature and Guardian Angle, ofcause only when it hurts at Warwick, if not just follow the guided

I have chosen Falsh because I'm happy to get away quickly and get to safety, some I can not really handle myself against several at once.
I have chosen Heal because it often has saved my butt and my teammates, heal is good when you do solo with Warwick.