Group resources based on cost ownership

Tags etc.

Regular cost reviews (at least weekly)

CapEx (Ahead of time planning) -> OpEx (regular reviews)

Estimate costs before you deploy (Pricing Calculator)

Use Cost Management features

Budgets and Budgets alerts etc.

Others:

Stop Resources when you don't need them

Use Managed Services (PaaS >>> IaaS)

Reserve compute for 1 or 3 years

Use Spot instances for fault tolerant non-critical workloads

Involve all teams - executive, management, business, technology & finance