Every year I donate up to 20 combined hours of pro bono career coaching to individuals and non-profit organizations. And, each year, participants approach me with the same question, "How can I thank you?". I typically reply by encouraging them to follow me on social media or refer me to other organizations that are in need of a career coach, but as the referrals increased, my bandwidth stretched resulting in much outsourcing (and fatigue - which is why I need coffee :).
As a huge coffee lover, you can simply treat me to a cup (or two) of coffee.
Giving back annually is something that will always be a part of my business model, so give if you choose to, but no pressure.