The only sound advice I can give is to conceptualize the absolute bare minimum of content, yet still successfully convey the message required for the piece.
Negative space is the star. The design elements will work to compliment that negative space. In such a way that the absence of design becomes the design itself. Elegant shapes, silhouettes, subtlety revealed in powerful planes of white.
Try taking a design you’ve done in the past. And start boiling it down, until you can remove no more without losing the message of the design. Then play with what you have left.