you just do it as it happens, takes like 10 seconds if that.  On the phone you may jot, Ronald 9;30 am 11/15 - Wants to have a meeting with Michelle.  Then you move on to your multi-tasking and doodling during the rest of the call.   If you are walking around and office and someone asks "can you order me this special calendar?"  you have the note book, jot it down and keep going!  I guess it gets easier and just second nature.  It is an extended to do list!