First and foremost - Stormraider's surge. It'll make life against Darius so much less frustrating. This also means using a champ capable of bursting him for 30% or whatever, but that's not too hard through most of the game. Totally invalidates his slows, AKA he can't keep up with you.
The main trick is small trades. I play Diana exclusively into him(And she dumps on him, FYI), so with her my goal is to get my passive primed, Q>R>W>Passive empowered AA>E>Run. This is enough damage to proc stormraider's, making his slows useless. Even if he hasn't used his pull until I run at the end, the stormraider's makes the slow from the pull not matter, and my E slows him in advance so I can still run.
In a close fight with him, say you're both at 15% and you KNOW you can kill him if that Q doesn't heal him - Don't hesitate to do something silly, like flash from the outside edge of his blade to the center of his model. No, it's not something do every time by any means, but things like this that seem counter intuitive can save you sometimes by denying him the heal of getting hit with the outside edge. Keep trades with him short, use any champion that can dump their combo on him and GTFO, or one that doesn't have to interact with him in order to lane(Hello GP). Don't ever let him get 3+ stacks during a trade. If he does, all he has to do is land a Q as you run then dunk you.
Bait him into using his Q near minion waves, walk toward him then walk away - Make him hit those minions and push the wave. Farm safely from under your turret while blasting him/running away with stormraider's proc any time he dares to show his big Noxian ass on your half of the lane.
Overall, since you don't want specific champ picks..
-Use Stormraider's Surge and any champion capable of dumping their entire burst in a short time to proc the Stormraider's and GTFO.
-Focus on small trades, if he gets you to 3+ stacks of his passive GTFO.
-If he engages with his pull, and you're above 50-60% health - Dump your combo real quick before you try to run. Chances are if you run right away you're eating a full damage Q blade.
-If you're under 50% health and he has his ultimate, stay the hell away from him. One stupid mistake and he's going to dunk you.
-Dodge that Q blade! If he's walking at you using it, walk at him! Get as close as you can and pop him in the jaw while he's spinning that axe harmlessly out of range. If you're in his face and he uses it while walking away from you, Walk away from him and get out of it's range. Keep in mind he'll almost always have more MS than you due to rage Procs, so you need to work in the opposite direction from him to avoid that axe.
-USE YOUR CC TO DISENGAGE. Most people want to use it to engage, and that works against a squishy. Not against Darius. He's going to pull you back and beat your ass. Save that slow or stun for your last move in your combo, and run away while he's stuck with the CC.
Best I can honestly tell you other than learn Diana because she straight invalidates him.