First, decide on the style of the speech bubble - whether it's round, pointed, or something more unique. Then, think about the color and thickness of the outline to make it stand out. Also, pay attention to the placement within the panel for better visual flow.
To make great comic speech bubbles, consider the character's emotions and the importance of the dialogue. Use different colors or patterns for special effects. And don't forget to leave enough space inside for the text without it looking crowded.