after years of trying every new "lifechanging" todo system, i finally found a system which i feel comfortable using and most importantly regularly go back and use it.
nirvanaHQ is a web implementation of the GTD methodology (getting things done). the GTD is a framework ( *** a bunch of processes and rules of how to organize your info *** ), which you can basically use a pencil and notebook to organize your tasks and prioritize them according to your needs.
nirvanaHQ extrapolates this methodology so you can use it on a computer and mobile app.
very helpful