Qualifications
Break out your laptop and FAFSA pin number, because marketing managers need bachelor's degrees.
There are three lines of thinking on what kind of degree you should earn. On the one hand, you want to be a marketing manager, so majoring in marketing makes sense, right?
On the other hand, the best marketers know their product really well, which means you might want to get a degree in, say, political science if you're interested in selling candidates to the voting public.
On the other other hand (how'd you wind up with three hands?), marketing management is a data-driven job, which means that coursework in computer science, economics, statistics, and mathematics can come in handy.
So, what do you do? Chances are, you have no idea what product you want to sell or what industry you want to work in at this point—you're just into marketing, dude. So, go for the marketing degree, but be sure you take the more quantitative coursework that will prep you for a marketing management position. Also, set yourself apart from the marketing pack by bulking up on your computer skills (think of all the advertising that's done online nowadays) and acquiring mastery of a foreign language.
Keep in mind, however, that your undergraduate marketing degree will only take you so far: Work experience is a must for this job. Find yourself a marketing, public relations, or sales internship or two while you're still in college; this should help propel you into the realm of post-undergraduate employment. Then, you'll spend eight to twelve years moving up the marketing ladder, working as a sales rep or buyer or product specialist, and taking on supervisory responsibilities for more and more underlings.
While an MBA isn't an absolute must for this job, some employers are going to want you to have that graduate business degree. You can find MBA programs with really excellent marketing coursework, better than anything that exists at the undergraduate level; graduate school is also a great place to make connections that can last your entire career.
Don't think you can blow right into an MBA program out of college, however; that's a rookie mistake, and you'll suffer if you don't at least have some work experience to serve as a filter for graduate classes.