To design effective microinteractions in a GUI:

1. Define the purpose: Identify the action or event that triggers the microinteraction.

2. Keep it simple: Use subtle animations and effects that don't distract from the main content.

3. Be consistent: Use a consistent design language throughout the GUI.

4. Provide feedback: Use microinteractions to confirm user actions or provide status updates.

5. Use visual hierarchy: Organize microinteractions to draw attention to important elements.

6. Test and refine: Iterate on microinteractions based on user feedback and testing.

7. Consider context: Design microinteractions that adapt to different contexts and user scenarios.

8. Use animation principles: Apply animation principles like easing, duration, and timing.

9. Make it responsive: Ensure microinteractions work across various devices and screen sizes.

10. Don't overdo it: Use microinteractions judiciously to avoid overwhelming the user.

Some popular tools for designing microinteractions include:

1. Adobe After Effects

2. Adobe XD

3. Figma

4. Sketch

5. InVision

6. Principle

7. Framer

By following these guidelines and using the right tools, you can create effective microinteractions that enhance the user experience in your GUI.