When you consider all the sources of work in your life, you should mentally categorise them. If they are on the 'Approved TM4T' list, they are probably Collection Points.
Collection Points - these are sources which we use to gather work into one place so we can process it quickly - all of the four TM4T sources are Collection Points. In order for Collection Points to be effective, we need to identify all of the Harvest Points - see below.
Harvest Points are physical locations where work routinely gathers, in a way outside of our control; for example pigeon-holes, answerphones and in-trays. To deal with these, add a regular task to your weekly plan - the frequency will vary depending on your school and role - to visit and collect work-items. These should then be dumped in your Personal In Tray (PIT).
Interrupts are sources which do not gather work together - instead they launch it at you unexpectedly: a mobile phone is a good example. As far as possible, simply remove these from your working life. Any interrupts which cannot be avoided should be routed to one of your standard sources listed above. An example might be a mobile phone call on the way to work - just jot down the task on your Ticklist to be tackled later. Other examples are post-it notes and text messages.