Timing is easy to recognize.  When the timing is right anyone who calls can get a meeting scheduled.  When the timing is bad, nobody who calls will get a meeting scheduled.  Then there are all the occasions in the middle – the timing is neither good nor bad – where by asking the right questions and getting them to recognize they might have an issue you can help with, you do succeed at scheduling a meeting.  These are the very meetings you want because early on, they aren’t talking with anyone other than you.