A big switch in my capacity for productivity took place when I switched my email folders and task list from a set of topic related folders, i.e. work, home, campus, staff, etc. to actionable items.
What I mean is that now I group things according to the action needed in my email. This is what my email folders look like now.
I also group my task list according to the action needed as follows.

Notes: A “Waiting for Response” folder has helped me immensely. Also, I’m way more productive if I do all my email’s at once and then all my phone calls for example. It’s not a perfect system but it’s helping my stay on task and it works for me. I still have projects that I work on seperately, because they involve multiple levels of action and communication.
Getting Things Done was trademarked by David Allen
What sort of Getting Things Done system do you use?
Other LTI posts kinda like this one:
Matt, what program do you use for your GTD system?
I use Things for Mac. It's kind of expensive, but it's been worth it for me.
I GTD’d my Gmail a while ago and that made a huge organizational difference. I’m so much better at tracking emails and not losing things. A more recent change I made was adding the multiple inboxes feature from Gmail Labs. This let’s me keep my actionable emails in a heads-up-display because I can still forget to pay attention to them when they’re hidden in a folder somewhere. The only thing Gmail lacks is categories of labels, but there are a couple Firefox extensions based on GTD specifically for Gmail that can solve that problem.