With that out of the way, here is some more advice: always have an alternative explanation. Better yet, have a way to test between the existing hypothesis and the alternative (the ever present 'Future Plans' section at the end of the poster). Don't get caught off guard like Paul Nelson.
During my session, several people asked me to provide "your alternative" to the problems posed in my poster. I must admit I wasn't ready for this question ... The overwhelming response from [everyone] was, "OK, Paul --so what do you propose to do?" Next time I'll be better prepared to step into the opening these questions provide.All right, I find this a little hard to believe. Anyone who has experience with presenting data should know that this is one of the first questions you will be asked. That's why you don't wait for it to be asked, you include it in the discussion. Not to mention that the scientific process is generally a constant comparison of the explanatory power of competing theories.
So kids, let this be your lesson. Know not only how you would explain your data, but how someone else might explain them.