The elements of most trusted systems are inboxes, lists, and a calendar. Your inboxes can be either physical or virtual, but everything that comes in (whether it's put there by you or by someone else) gets processed and either thrown out, filed, or turned into actions which you then put on lists or your calendar.

You have many lists: a list of projects, a list of actions, lists of Next Actions, etc. How many you keep and the format in which you keep them are up to you.

The calendar is for things that must get done at a specific time, and they can either be appointments with others (i.e. meetings) or self-imposed blocks (i.e. I'll work for 1 hour on one aspect of one project on Wednesday at 3).

The whole thing is very customizable to your own preferred set of tools and your own methods. However, it sounds like you haven't read GTD yet; to really understand the process you should read David Allen's book. No short summary on a Web forum will do justice to David's in-depth presentation of these ideas.