In recent adventures, I've often employed and supported using the meta level (i.e. thinking, joking and referencing about the game's contents with reference to our cultural context) for everyone's enjoyment. With my last group, this has worked very well - we've all had a lot of fun and a very immersive game, with tempo and game style oscillating between the two layers in 15-30 minute intervals.
With my current group, I'm having problems establishing clear and natural transitions between the two levels. While we principally agree that being immersed and being meta are both desirable, we often get out of sync and thereby disturb the rhythm, with a player joking in scenes that had very good immersion potential.
I've considered physical aids (like using a hat to indicate mode) or scene-based playing (with clear beginnings and ends of scenes as in a play) for leading the game more clearly and thereby aiding synchronization, but this seems somewhat clumsy.
Are there more elegant ways of handling immersion-meta transitions?