Darius is a strong champion that does well through all the game if going ahead of his enemy and he has the right skills to accomplish that.

Your best Friends:
Q
Passive
W+aa

Early Game Main Objective: Farm CS while blocking the enemy, this means: make him regret any attempt to hit a minion while you are around.

Never overpush a line, you dont want to end up destroying a tower before being able to gank properly and seriously crippling your top lane enemy(making him have low kda+low cs in comparition to the other players)

now you have 2 actives that cause soft cc and 2/3 actives deal extra damage, now you have enough dps to deal with any enemy that tries to escape avoiding any guilloting to force a kill on the running enemy :V