Tips for switching?

My partner and I have a vanilla relationship plus we are relatively new D/s, however we do not practice the power dynamic at all times. We have been discussing how to practically switch between these roles in a sense of communicating to the other that we are wanting to switch? Or to signify we are now in the power dynamic? For example, we may be at a restaurant and I'd be keen to switch to D/s. Is it a simple "code" word? If it is pre-planned, is it a certain item of clothing or accessory we would each wear? Would love to hear any advice along these lines, or in general on how to move between the two dynamics. Thank you!