Best way to pull off a "success" message?

[eluser]ekeretex[/eluser]
Ideally (even for displaying error message) you should not show your status messages on the same page as your post.
This elimates the danger of double submission and the alert box that pops up if a user refreshes a page after doing a post.
Details here and here.

I personally use the OBSession session library, pass all status messages (errors and success) into a flash variable, redirect (to the same page, sometimes) and then display the status messages.

This method ensures the page the user sees is always displayed via a get.