I run into a lot of people trying to switch careers and join a startup. They're trying to get product positions and marketing jobs in particular, but they don't have any prior experience. That leaves them in the infinite loop of not being able to get the job because you don't have experience, but not being able to get any experience, etc, etc.
It's a solvable problem. You can do nearly absolutely anything within one or two years time--as long as you put your mind to it and construct a plan. I'll talk more about this at my upcoming General Assembly talk, but here's the outline.
One of the inspirations behind the company I started in the career development space was a conversation I had with a Fordham student. He was interested in venture capital and was a year away from graduation. I realized that a position at Union Square Ventures was going to be open in a year and that he had a terrific chance of getting it. He seemed perplexed that they'd even consider hiring someone out of school. What I told him was that no other people had a year head start. It was unlikely that *anyone* was thinking out a year ahead that getting that particular job was their goal. He could decide right then and there that he was going to get that job in one year--he just had to do all sorts of stuff to be the number one recruit--after figuring out what that was. It was an exercise in reverse engineering.
This can apply to most jobs--save for things like coding and design that tend to be more hard skill based. However, I'd make the case that if you really did dedicate yourself to something, you could make a lot of headway in two years time--especially if you had some natural inclination. Me, I can't draw my way out of a stick hat, so I'd be a lost cause--but a creative person could do a lot with design classes in two years.
In any case, you're going to have to start out with a very detailed job spec. You need to know exactly what someone in this role is doing now--and there's no better way to do that then to just ask. If you want to be in venture capital, ask a bunch of junior VC types what they actually do all day, and ask a bunch of partners what they expect the junior VC types to do all day (I wonder if this would come anywhere close to matching up.) Write down all the tasks done, skills used, etc. and see which ones overlap the most. Those are the "requireds" and the rest are the "preferred". See if you can group these attributes into types. Some product managers might be more technical, working on feature requirements and interfacing with the engineering team, while others might be more like brand managers who are the GM of their brands. Not every employee needs to be the same, but everyone needs to be awesome in some way--just figure out the various types of awesome that fit into that particular role.
Your job description now becomes your checklist. When a product manager tells you that they monitor and track analytics using the following pieces of software, now you have to go out and learn how to do that. That could mean taking classes that cover Google Analytics, asking different product people to sit down with you for 30 minutes to show you how they use the tool, or maybe even contacting someone at Google to invite them to run a class on Google Analytics best practices not just for you, but for others trying to do the same thing. Service providers are generally apt to do this kind of thing--showing you how smart they are by teaching you tips and tricks for the stuff they use, knowing that a lot of people won't have the time to do this on their own, so you'll probably wind up paying them to do it.
There's also a ton of content out there. Just start looking for blog posts on "10 SEO tips for startups" or "How to write a marketing survey". The web is a big open textbook written by practitioners.
Now you need some practice. You've learned what exactly other people do, and how they do it. Now you need to get out there and start offering it. Unfortunately, you're still stuck with the experience issue. Then again, how many lean startups are out there with lots of stuff to do without the time to do it. If you were trying to teach yourself to become a UX expert, and you've interviewed a bunch of people about conducting user interviews and looked up every great blog post on the subject, is it really that hard to find a startup willing to let you do this with new and existing users? Just ask around at the companies you like and ask them whether or not they've actually sat down and tried to work through real user interviews. I'll bet you get a lot of "Yeah, we listen to our users" or "We showed it to some people before we launched and they liked it". These are prime candidates, because they haven't really committed to doing this the right way--and I'm sure they'd let you conduct user sessions.
You'll also want to journal what you're learning. Writing about the techniques you learned about, where you learned them, and even what set of skills you found that most professionals considered to be important accomplishes three things.
First, it acts as a mechanism for synthesizing what you've learned. You'll never learn so much as when you have to teach someone else to do something--and blogging about something you just learned is a way to do that.
Also, sharing the resources you found will also encourage others to add to the list. When you post the most useful blog posts on sales that you found, people will undoubtedly leave others in the comments. Sharing knowledge leverages the community by encouraging others to share back.
Lastly, it helps your brand as a continuous learner. When you do apply for a job, being able to show someone what you've been doing over the last year to learn creates a very favorable image of you that will undoubtedly set you apart from others. You set a goal, did the leg work, and executed well. It will give someone the confidence that you can learn new things with the same zeal and that you'll work hard to achieve goals.
When you offer your newly learned skills for free in a project (something you can do while you have another job) and you write about it, if you create a good public case study, undoubtedly others will want you to do the same for them. If you spent a Saturday afternoon conducting user interviews and you learned a lot about how people do something on a particular site, leading to some really interesting insites, you're going to have your Saturdays booked for a while. Eventually, you're going to be able to say, "Hey, I'm actually pretty swamped right now" and the response will be "We'll pay you!" Bam. Welcome to being a paid consultant for something you didn't even know how to do a year ago.
It's also important to take these projects and loop back with the professionals you've talked to. Take the sales plan you wrote up for a startup back to the head of sales for a more mature company and get their feedback. Iterate based on their feedback and your experience. With each new project you do, you're going to get better and better at it if you incorporate your learnings into a good feedback loop that improves the way you execute.
This doesn't necessarily have to take 1-2 years either. I'm sure someone who tries this will wind up with a job after six months. I just don't want to promise anything too soon, because becoming a top tier professional takes a lot of long term determination.
Oh, and by the way, I've given this advice to tons of people over the years, and rarely does anyone ever take it--so if you do decide to do this, let me know, so can at least have more than one example that it works.
One thing that's important to note that to imply that anyone can do just about any other job with a year of work doesn't necessarily mean they'll become an expert. In fact, I once wrote a post called "Respecting the Craft" about how too many people think they're a smidgen away from greatness in a lot of fields. No, this post is meant to encourage people to put in the work that gets them in the door somewhere--to start out. Reading a bunch of blog posts isn't a substitute for a career's worth of experience--but it will definitely, when put into practice, get people focusing more on your projects then how you look like all the other MBAs out there that they've met.