What are the most effective strategies to reduce cloud infrastructure costs in Microsoft Azure without affecting performance?

I work with multiple small and medium businesses that rely heavily on Azure for their daily operations. While the cloud provides flexibility and scalability, managing costs has become a major challenge.
I would love to hear from professionals who have successfully optimized Azure costs — for example by using reserved instances, right-sizing VMs, storage tiering, or automation scripts.
What specific techniques or tools have worked best for you, and what common mistakes should be avoided?