Introducing new characters to the story?

[Ola Matagi]

How do you introduce new characters to the story in interesting yet subtle ways so it doesn't seem like you're just bringing them in just for the MCs purpose in achieving their goal when you really are.

 

[Kitten Tamer]

If its a second MC, then I tend to introduce the idea of them at the beginning then move onto the other MC. So in the book I'm working on now, the second MC is at the very start of the book, but you don't get his name or looks, just that his in trouble and running from the police. Other characters I tend to bring in through the MC. So the MC could say,
"I've gotta get my bike fixed. We won't get far with the tank leaking. Apollo should be able to do the job."

By mentioning the character through the MC, it's more easy to the reader. You see what I'm saying?