If you took a marketing class in college, you probably remember the four Ps of marketing. When I was an undergrad, these four words were burned into my brain: Product, Price, Promotion, and Place.

Most modern marketers recognize this formula is outdated, focusing too much on the product and not enough on the customer. But in addition to this lack of customer focus, it entirely misses another P: Plan.

In a survey of small businesses, Intuit Quickbooks found 65 percent of owners admitted wishing they spent more time and money on marketing, and 67 percent wished they had written a better business plan when first starting out.

To actually make money, you need a customer-centric plan. With this, you can keep your budget in check, track your progress, and optimize your strategy.

A modern marketing plan needs to include answers to these four questions.

1. Who are you talking to?

Customers come first; without them, you don't exist. Get to know them, learn their needs, understand their concerns. How do they consume information? Where do they search for solutions? Why do they make purchases?

At my company, we've learned a lot about our customers. How? Through feedback from our customer service reps, customer surveys, purchase data, simple Google searches about their businesses, and by looking at who engages with us on our social media channels. A business's Facebook or Twitter profile can tell you a lot about what matters to them.

2. What are you saying?

These days, there's a startup for almost everything. For example, mysubcriptionaddition.com features over 300 "Food" boxes. How do you differentiate yourself in such a crowded market?

Let's look at three of the big ones -- Blue Apron, Plated, and Hello Fresh. They all provide the exact same service. Even my local grocery store sells pre-measured meals. What makes them different?

Plated emphasizes the ability to customize a subscription. Blue Apron is eco-friendly and sustainable. HelloFresh is all about the love of cooking.

You need to do competitive analysis to learn how you stack up against your competition, and then tailor your message (and product) based on the results. You must make yourself different in a way that's sustainable. Simplify this message, and then write it down.

3. Where do you say it?

Once you have your customer-focused market positioning and messaging documented, you're ready to choose your channels and map your resources accordingly. You might use social media, digital (or print) advertising, email, or local events. Since you know your customers so well from your earlier research, you'll focus on channels they use.

My company's customers aren't very active on social media... except for Facebook. They're all over Facebook. When we first started marketing on social media, we promoted content on Twitter, LinkedIn, Google+, Pinterest, and Facebook. But we've gradually adjusted our strategy to make it more effective. You'll need to do the same.

Chart out who will manage which channels, tasks, and programs. And be realistic with your budget -- you need to invest to see results. But watch what you spend.

4. How do you know it works?

As well-researched as your marketing plan is, you'll never really know what works until you try it. You need to set growth targets and track your results. Once you collect data, use it to optimize your marketing plan.

If you don't track your performance, you'll never know if your marketing is effective. Don't bring back the subjectivity of the "arts and crafts" days of marketing.

To learn what resonates with your audience, A/B split-test different versions of your work and track some of these data points:

  • Open, click-through, and conversion rates
  • Length of the buying process
  • Which channels have highest ROI
  • What types of content gets the most engagement
  • Reasons for leaving/not returning as a customer
  • Overall revenue and profit
  • How your results compare to industry benchmarks

With these four elements, you'll have a marketing plan that will help you connect with customers, gain loyalty, and grow your business.