I am playing Darius, for me he is the one of the most fun to play champion, but he is also strong as hell. If you build him properly , you will never loose your lane .

Pros
True damage ultimate.
Extremely high damage even if you build him as a tank .
Even he got nerfed is still OP.
Low mana costs.
Can easily fight against more enemy champions.


Cons
He has no escaping skills, except flash .
Very focused, even if is tanky.
Very weak against ranged champions.( or at least until level 3 )
Strugle to get back into the game if failed hard early
Not that good without Zilean in team :)

These are very very important because he has no escaping skills.
The best choice is Flash and Teleport.
You can also take Ignite and Flash or Flash and Exhaust

This is the most important, you should have 75 creeps at 10 minutes or so.
Darius is very easy champion to farm with especially when he gets Hydra.

This is a guide for ranked games so I will tell you everything you need to know.
Early game

- First of all you need to have a decent creep score. It's better to keep poking your enemy but in the same time do last hits . As Phreak said in the champion spotlight stay between your minions and the enemy's minions. Look for nearby fights and focus the most squishy champion, like their lowest health champion. (still available in midgame)
Midgame

- You shouldn't be top lane anymore, your enemy's turret should be already destroyed so go and help you teammates. Gank mid/bot and try to countergank. If your team is doing well ask your jungler to help with the Dragon .
Lategame

Here a single one mistake can ruin the entire game, so try not to make mistakes.
Even you aren't a support you should have 1-2 wards with you, if you have space in your inventory. Place some wards in your jungle if your support doesn't to prevent the baitings or traps .
When you don't see the enemies on the map there are 4 possibilities where they could be:
- In their jungle
- Taking Baron / Dragon
- Preparing a trap
- Fapping/Throwing a party in base

DO NOT have walks farming when you don't have vision in your jungler because you can destroy a game. Just stay in the base and farm.

If your team is wining:
Don't get greedy and try to make traps, like hiding in a bush where they haven't got vision and wait for somebody, after you caught one of them the game is 5vs4, for about 1 minute. Profit.

Teamfights
Here you have to respect 3 rules:
- Do not go in the fight alone.
- Protect your AD carry and your AP caster.
- Focus the enemy AD carry or/and the AP caster (only if your team has somebody to protect your AD carry/AP caster.)