That is one hell of a broad question.
It depends on your workflow, how your jobs come in, who has experience, etc. etc.... there are too many factors to say "THIS IS THE WAY TO DO IT."
I would suggest going to a training course - they are more helpful than you can ever imagine.
Depends on your industry. What I might tell you to do as a large format prepress tech is not what someone in the 4-color world will tell you.
Want to narrow this down some? Designers don't usually work UNDER a Pre-press lead (Though one could wish, LOL). Designers work under Art Directors and Creative directors, usually, in group situations.