“People often remark to me that “GTD does take a lot of discipline!”
Actually, it doesn’t, any more than taking showers and brushing your teeth require discipline, once the initial unfamiliarity has been overcome. How long does it take to get there? As long as it takes.
You’ll be another day older tomorrow, no matter what. So just keep returning, when you stray. Write things down. Decide outcomes and actions. Organize and review them. And you’ll feel more and more uncomfortable when you don’t.”
—David Allen
I would recommend checking out http://www.Gtdagenda.com for an online GTD manager.
You can use it to manage your goals, projects and tasks, set next actions and contexts, use checklists, and a calendar.
Syncs with Evernote, and also comes with mobile-web version, and Android and iPhone apps.