Every planner wants to be able to say their event was a success... But how do I know?

Every planner wants to be able to say their event was a success... But how do you know?  What is the most effective way to find out if your event was successful?  Most importantly how do you use the information collected?

There are a couple levels to measure your event.  The tools people tend to gravitate to first are numbers.  Is ...

We’re really trying hard to cut costs so we’re only spending money on the essentials for our retreat this year.  How do we get the most out of our retreat without over spending?

I have heard the following questions from meeting planners lately: "When my ministry is seeking to make the most out of the retreat do we even have time for extracurricular activities?" "We're really trying hard to cut costs so we're only spending money on ...