There's no getting around it. If you don't have a portfolio, you won't get a job.
If you're a creative person, your portfolio will get you your first job and every job after that. Whether or not you get to work for an agency or advertiser that does "good stuff will depend almost entirely on whether or not there's "good stuff in your book.
These facts hold true regardless of what stage you are at in your development, whether you're a rookie creative person just looking for a chance to work on anything, a junior creative person trying to get a shot at working on the "good accounts," or someone with years of experience under his belt looking for a job as a creative group head or creative director. The kind of job you get will always depend on the kind of work your portfolio shows you can do.
Sometimes, later on in creative careers, a reputation built on many years of consistently brilliant work precludes the need for a formal portfolio; but more than 99% of all the creative people in the business will have to show a portfolio for every job they ever try to get.
Basically, there are two kinds of portfolios you can put together.
1. A portfolio to impress your mother.
2. A portfolio to impress a prospective employer.
In your mother's portfolio you put everything you've ever done, including your first crayon picture of Santa Claus, the snapshot you took of your Aunt Daphne and Uncle Wilbur at their Silver Wedding Anniversary Party, the clever little captions you wrote under the pictures of your friends in your high school yearbook, and a cross-section of term papers you wrote in college. Naturally, you'd include every piece of advertising you ever wrote, plus all of the drawings and thumbnail sketches from which they came. Make sure you've got at least two hundred layouts, five hundred and sixteen headlines, and every idea you ever had for anything. Your mother will be tickled pink. It doesn't have to be organized; you can shove it all into a paper bag if you want. After all, your mother absolutely adores seeing everything you've ever done.
Prospective employers don't.
Prospective employers are very busy people. They look at lots and lots of portfolios. And unlike your mother, they have a lot of things they'd rather do than look at yours, and not because they don't like you or are predisposed to think your book isn't worth their time. Chances are they started their careers the same way you're trying to start yours. They know how much work it takes to get started. They understand the insecurities you feel. But they just don't have time to spend hours upon hours on every portfolio they see. And, while showing your portfolio is the most important thing you do, looking at portfolios is only a small part of what they do. They have to devote the rest of their time to things like getting new clients, servicing the clients they have now, doing ads, and generally running a business.
With that in mind, the portfolio you prepare for a prospective employer should be neat, well organized, and shouldn't take too long to look through.
It should contain quality. Not quantity. Leave out anything that isn't absolutely relevant to your finding a job.
A portfolio of ten pieces of your work should be entirely sufficient. If an interviewer can't tell whether or not you'd be worth hiring after seeing ten samples of your work, he'll either ask to see some additional specific things, or he's not worth working for anyway. Besides, the simple truth is that if you don't have a portfolio that is relatively short, neat, and well organized, a lot of creative directors, group heads, and whoever would rather not take the time to look at your portfolio at all; because if you don't care enough about your own book to make it look like you're proud of it, and if you don't care enough about yourself to try to look professional, they probably won't care to have you around.
That may sound cruel. But it's true.
Forget about the media plans, marketing plans, and creative rationales. Media people write media plans. Marketing people write marketing plans. And interviewers know just as well as you do those creative rationales can be written after a campaign has been created to prove that you knew what you were doing.
Exactly what do you put into your portfolio?
If you want to get a job as a print producer, your portfolio should be filled with pieces that you've produced: ads, brochures, posters, any printed material, even if all you have are school projects.
If you want to be a broadcast producer, your portfolio needs samples of commercials that you've produced, even if they're commercials you did in school. If you don't have any commercials, include storyboards or still photographs.