I have been thinking about ways to make my current GTD setup more efficient. One thing that makes it hard to keep on track and focus are interruptions and the way one has no control over them.
At work, we use the standard calendar features which let us invite each other to meetings, automatically marking that up in the calendar as busy time slot. While that is a convenient feature, it basically lets other people be in charge of your own calendar and your own time.
So what can be done about this? Since I use the GTD methodology, it would be very convenient solving the problem with the tools already at hand. I decided on a set of rules to makes this problem (at least to some extent) go away.
During my weekly review, which is usually done on Monday mornings, I activate projects and actions which will require my attention for the coming week or so. Part of the process is to do a rough time estimate for most actions, and some actions requiring at least one hour of consecutive time are then inserted into the calendar when I want to work with those particular actions. Smaller actions which are similar (preferably the same project or tool) may be grouped together in the calendar to form a longer session. This makes it much easier to focus on the tasks at hand, and it makes your colleagues aware of your sessions.
As a pleasant side-effect of doing this, you will appear busy in the calendar where you have planned these working sessions, meaning that people will be more hesitant inviting you to attend meetings during that time. I usually make a note in the calendar on which project I will be working on, which makes the project manager for that particular project more keen on not interrupting your flow.
This post is inspired by The Chokehold of Calendars, where you can read more about this method, and then maybe implement it yourself.