Search engine marketing, specifically paid search, can be the fastest way to generate leads with a positive ROI. The challenge, however, is doing so with a healthy cost per acquisition (CPA). Indeed, there's no point in running search ads if they're not profitable.

We recently conducted a study of 30,000 paid accounts to see what affect machine-learning (ML) had on performance. It turns out that ML can help reduce CPA while increasing conversions at the same time.

We also uncovered lessons you can apply to your paid search marketing, no matter what additional technology you apply.

Here, I'll share eight techniques you can use to boost conversions while reducing the CPA of your ad campaigns.

1. Use remarketing and retargeting (the right way)

Although it's not a direct contribution to CPA reduction, remarketing can help you capture bounced visitors at various stages of the funnel.

For example, let's say a prospect visits a landing page to book a demo from a PPC campaign. They spend some time reading the copy but eventually bounce. Instead of letting them get away, use remarketing to capture them higher up the funnel. You can do so by using the AdWords display network, Facebook ads, and other visual-ad platforms that allow for retargeting.

I recommend these three landing-page approaches:

1. Thought leadership: This approach positions you as a credible authority in your space. Your offers might include whitepapers, e-books, and other useful content on landing pages. The idea is to guide audience members through their journey, helping them to figure out what they need to solve their problems.
2. Credibility boosters: Showcase your expertise and credibility with testimonials and case studies. These landing pages must still put education first, using customer stories to build your credibility.
3. Conversion: Once users have worked their way "down the funnel," it's time to drive them to a sales page—demos, free trials, price comparisons, and even contact forms.

Once your landing pages are set up, you need to create ads that grab attention. Start this process by creating four variations. When setting up your campaign in AdWords, ensure you select "Rotate indefinitely" under Ad rotation:

Creating several ad variations allows your audience to decide for you which they're most receptive. By letting the variations run for a month, you'll see which generates the most conversions.

2. Remove "no sales zones"

If you're using an ad platform (e.g., AdWords) that allows location targeting, it's highly likely that you're serving ads in "no sales zones." These are simply locations that have generated little to no conversions over a period.

It's best to track those areas over the course of three months. Identify them using Google Analytics. Simply head to Audience > Geo > Location and, under the drop-down (illustrated below), select Goal: Conversion Rate:

Dig deeper with city-level targeting no matter how large or small your organization is. Unless you're generating little amounts of traffic at a country/region level, this is one of the quickest ways to boost the ROI of your ads.

3. Give your quality score a boost

Optimizing quality score is best-practice, and the fact it would be on this list is nothing new.

But how it's optimized, especially for B2B organizations, is key. It all comes down to building better campaign structures.

Instead of simply optimizing your ad creative, break down your campaigns to create highly relevant keyword groups. Doing so will not only improve how effective your ads are but also boost clickthrough rates because you'll be serving ads relevant to the searcher's intent.

Using this approach, Audi boosted its CTR by 22% while cutting down cost-per-lead by over 50%.

James Parsons puts it best in his article: "Ad variations in ad sets can help a lot with keeping costs down. Instead of targeting one massive audience with one ad that may or may not be very good, break your audience down. Target different segments of your audience with different, more tailored ads."

Prioritize this approach by identifying your highest performing keywords in Google Analytics. When creating separate ad groups, ensure you include all three match types, like so:

Make sure your copy is compelling and, more important, relevant. Make these ads relevant by including the target keyword in both headlines.

4. Rigorous and ongoing A/B-testing

You should be continually experimenting with and optimizing your paid ads. To gain better results, you must tweak various elements of your campaigns, including images, calls to action, and landing pages.

Before we get into some A/B-testing ideas, here's a seven-step process for setting up experiments:

1. Define your success metric: What will define the success of your campaign? For example, are you optimizing for clicks or conversions? Write down the test goal and choose a metric that serves that goal.
2. Write a hypothesis: The clearer your hypothesis, the better the outcome. For example, if you were coming up with an experiment for your ad copy, a possible hypothesis could be "Including a deadline in the call to action will increase conversions 15%." Define your variable and create a hypothesis.
3. Create test ideas: Come up with as many ideas as possible. Some call-to-action ideas are "include a deadline," "create scarcity," or "highlight client results." Brainstorm as many as possible.
4. Prioritize: Use the ICE framework to prioritize your tests: Impact, Confidence, and Ease. (Check out this guide from Trello to learn more.)
5. Determine sample size: What is the sample size for each metric? For example: the minimum number of clicks, traffic, or conversions needed before your test ends. Define the minimum sample size for your experiment.
6. Begin testing: Run your test for at least a week. Don't end it once you see results. You need as much data as possible across different behavioral variables. In other words, people behave differently at different times and days of the week. Once the test is over, use a calculator like this one to ensure statistical significance, and keep running your tests until they are statistically significant.
7. Analyze results: Compare the results of your test to past performance. If the results are better, then the test was a success. If not, repeat the process until you see improvements.

That seven-step framework can be applied across all marketing channels. For optimizing your paid ads, here are three ideas to get you started.

A. Multiple Descriptions Using 'IF Functions'

Your experiments should test not only new copy variations but also new and emerging technologies. Using the AdWords IF function, you can create separate descriptions for mobile and desktop devices:

B. Pricing Variations

Including pricing can be a blessing and a curse. Some visitors may appreciate the transparency, whereas others may be turned off at the reminder that they need to buy something. In this example, conversions increased by simplifying the price: