Making phone rings - is the goal most clients want from SEO.
Here are the SEO related steps I take to ensure the most calls, and the ability to track them back to SEO and website efforts:
- Add Phone Number in Top Right Header of All websites
- Setup a Dedicated 'Conversion' Landing page with a big call to action and phone number. The phone number should be setup using a call tracking service like https://calltrackingmetrics.com/ (that one's my favorite $5/number per month)
- Run a Google Adwords campaign to the landing page above
- Report to Client OR your internal business team the result each month. Tweak and tune to get better results.
Those are the main steps I do for each of my client accounts to get the phone ringing, and make sure it's tracable back to the SEO/online marketing efforts.
The end goal of course is to show clients that an increased investment in SEO leads to more calls! Than everyone wins 
Hope that helps