Poster design is a visual communication tool that uses graphics, text, and images to convey a message or promote an idea, event, or product. Here are some key principles to keep in mind when designing a poster:

1. Purpose: Identify the purpose of your poster and the message you want to convey. This will help guide your design decisions and ensure your poster is effective in achieving its goals.
2. Hierarchy: Use hierarchy to guide the viewer’s eye through the poster and emphasize the most important information. This can be done through the use of font size, colour, and placement.
3. Contrast: Use contrast to create visual interest and make important information stand out. This can be achieved through the use of colour, font weight, and texture.
4. Balance: Achieve visual balance by distributing elements evenly throughout the poster. This can be done through the use of symmetry or asymmetry.
5. Typography: Choose a font that is legible and appropriate for the message you want to convey. Use a limited number of fonts and font sizes to create visual consistency.
6. Colour: Use colour to create visual interest and convey emotions or mood. Choose a limited colour palette and use colours that complement each other.
7. Images: Use images and graphics to convey the message and create visual interest. Use high-quality images and graphics that are relevant to the message you want to convey.
8. White space: Use white space to create visual balance and allow important elements to stand out. Don’t overcrowd the poster with too much information or graphics.

Remember that poster design is a creative process, so don’t be afraid to experiment and try new things. Test your design on different audiences to see how effective it is in achieving its goals.