can you give me some tips for creating posters ?

If you can give me some information about the poster, I can describe how to create it. The message the poster wants to give Style of poster Size of the poster

about fitness

Focus on a bold, eye-catching headline that captures your message, and pair it with a clean design that uses space effectively to guide the viewer's eye. Don't forget to balance color and typography to make your poster stand out, yet ensure it remains readable from a distance.

I would say use AI for the art - if you're not an artist. For the text and the composition, look at some relevant, successful posters and imitate them. Try to use the same composition, size, fonts...