The core principals that drive inbound marketing are straightforward, but putting them into action requires real expertise. Every business wants to climb the search rankings, but dancing with Google means learning a new step with every algorithm update. Making a blog post or two a week sounds simple enough, until you realize that each blog post needs to be tailored for SEO, promoted in the right places, linked with appealing lead-generation offers, and planned far enough in advance that you have a steady, fresh supply of relevant content.

Choosing an inbound marketing agency is the best way to make the most of your marketing budget, and frees you up to invest your time where it's needed most. The trick is finding the right agency for your needs, and I've got a few proven tips to help you find the right match.

Does your inbound marketing agency know your business?

Most marketers are interested in honing their skills. They read the latest business news, stay up on marketing trends, and work to develop a broad understanding of a wide selection of industries. While all of that broad knowledge is useful, your best bet is to look for an agency that truly knows your business, and your industry. This will be one of the most important criteria of your search, because the subtle differences between industries (and audiences) have a major impact on which marketing tactics are most effective.

• The good news is that this type of experience is pretty easy to spot, once you sit down for a conversation with a potential agency.

• Look for an agency that delivers a plan tailored to your business, and shows you why each tactic is a fit. There should be a clear connection between the types of prospects you're looking for, and the tools an agency proposes to reach them.

• If you're having trouble forming an impression, don't be afraid to ask marketing questions that require specific industry knowledge to answer. It's not much different from interviewing potential employees.

Is integrating marketing and sales a priority for your company?

The line between marketing and sales is more blurred than ever. You can't – or at least shouldn't – plan for one without considering the other. Look for an inbound marketing agency that makes integrating your sales and marketing processes a top priority. Your sales reps should understand the impression that your marketing is designed to make on new prospects, and your marketing people need to work with your sales team to ensure that they're targeting the right prospects, at the right time.

• In addition to priming prospects for your sales team with a positive message, your marketing should generate tons of prospect data that will be useful for your sales team when converting prospects.

• What data points do your reps depend upon most to convert prospects? Just as importantly, how does that information make it from your marketing team to your sales reps efficiently? Tightly integrated sales and marketing allows both sides to thrive.

Does your inbound marketing agency adapt and iterate over time?

If a marketing agency tells you that they have a locked-in plan for how to market your business over the next two years, proceed with caution. Or maybe don't proceed at all. Marketing, especially on the digital side, evolves far too quickly for a rigid long-term plan to be effective. Outside of generating new business, the biggest benefit of inbound marketing is all of the valuable data it supplies. You want a marketing agency that puts that data to work.

• Look for an agency that will review, update, and iterate your marketing plan based on new data every few months, at least. This is also an area where sales and marketing integration is critical, because updating your marketing affects both sides.

• Iteration doesn't mean throwing out your marketing plan every few months. There's plenty of value to be gained on the margins, so subtle changes based on accurate, current data make a big difference over time.

• New tools, tactics, and trends are always emerging in the broader marketing world. An agency that knows your business will also know when a new tactic is a fit for your needs, and separate the good stuff from the fleeting trends.

The overall ingredients are consistent, no matter your industry. Set your sights on an inbound marketing agency that knows your businesses, values the crucial interplay between marketing and sales, and aims for constant improvement over time by iterating your marketing plan. With a solid foundation in place, you can be confident that your inbound marketing agency will deliver a consistent, positive return on your investment.