To introduce characters well in a comic, you could start with a close-up of their face to show expressions and emotions. Or, you could have them interact with other known characters in an interesting way. Sometimes, a backstory snippet at the beginning can also make the reader connect with the character quickly.
Well, one way is to show their personality traits right away through their actions or dialogue. Another is to build up some mystery around them to make the readers curious. Also, you could introduce them in a visually striking way, like with a distinct outfit or a special background.