I've been thinking of this topic for a little bit, now. I know this topic has been discussed before, but it's been a while and I'm hoping other, more experienced writers and Role-players might provide some input.

Since this is RPing and not writing a novel, the decision to do either may be difficult or even unknown. 

When should you show?
When should you tell?
Which do you prefer to read? 
In which areas of RPing do you prefer to see either/both?
Do you have any examples of really great/impactful "Showings"/"Tellings"?
Is it appropriate to switch from one into the other? When?
etc.