Saw lots of Darius talk earlier. I think he's a good champion, but he has some restrictive win conditions. If you don't play things right, the late game can be pretty discouraging.
You need to win your lane quickly. With his bleed, his pull, and his ult, you are an all in machine. Even little buttholes like Teemo don't affect you because you can burst him without auto attacks, which is nice.
Anyway, you push your lanes hard, making sure to keep wards up. They will try to gank you often, because your whole goal is to snowball and then roam, and smart teams will try to prevent that from happening.
Go Hydra first. It allows you to push hard, get some life steal and regen, and get a little AOE. From there start tanking up a bit. Darius is one of the few champs where Sunfire Cape is a good idea. Build that next along with Randuins while getting your boots (I like Merc's). From there, you can go back to building damage and try to end the game as quickly as possible. Trinity Force is decent, Maw is awesome for jumping into team fights and surviving long enough to cause problems.
Your main role in the team fight is to tank your way to the ADC, pull them in, and execute them with your ult. On the refresh, hit their mage or whoever else is dealing big damage. You'll probably die, but it's generally enough to win the fight.
Darius shouldn't die much early, but it's not the worst thing if you're dying in the big fights late as long as you get his ult off twice. You're probably going to push things into your team's favor unless they're incompetent.
One thing to remember, on his Q it does way more damage to enemies on the edge of your range. Also, the indicator on his grab is garbage. The edges of it are outside of its range, so beware of that. I've missed a lot of pulls on enemies that were clearly within the indicator.
Darius is fun! He's a little bit "Baby's First Top Laner," but it's ridiculously fun in the mid game when you're snowballing and executing people right and left. Play him like Renekton. You have to finish the game before you become irrelevant with bad scaling.
