With Darius you will want to shut down the other solo top as soon as you get your pull. Help from your jungle is not necessary but can be helpful. You always start with your q and get your e second. Once you have those you can typically kill whoever you are laning against. You need to either flash then pull then q and ignite. Or you can lure them, pull q then ignite and flash if they start to get away (that is the best strategy when facing a faster champ i.e. Teemo or Master Yi). If you get this right you have secured your lane. After that just make sure you use your ulti when you know it will get a kill since it resets if you do. Darius is a clean up champion and can be a huge asset to team fighting. He can secure kills when someone is getting away. So be prepared to hear yelling about how you ks to much.