any relevant get started tips for AWS security ?

AWS Security is a very broad topic and subjective thing.

AWS is one of the best IaaS provider to ensure security of your resources. It provides options like AWS Security Group, Secure Key-pairs, Groups and users with IAM, virtual private network and many more offerings to make your application secure.

For the US government organization AWS provides Gov-Cloud region which is compliant to Govt specifications.

Each of the above it self is a big topic but refer  AWS Security whitepaper at the the AWS security site for more information on AWS security.