Add minor tips to CloudFormation

README.md

@@ -1499,6 +1499,8 @@ CloudFormation
 -	CloudFormation allows the use of [**conditionals**](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/conditions-section-structure.html) when creating a stack.
 	-	One common way to leverage this capability is in support of multi-environment CloudFormation templates – by configuring them to use ‘if-else’ statements on the value of a [parameter passed in](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/parameters-section-structure.html) (e.g.  “env”), environment-specific values for things like VPC IDs, SecurityGroup IDs, and AMI names can be passed into reusable generic templates.
 -	**Version control your CloudFormation templates!** In the Cloud, an application is the combination of the code written and the infrastructure it runs on. By version controlling **both**, it is easy to roll back to known good states.
+-	Avoid naming your resources explicitly (e.g. DynamoDB tables). When deploying multiple stacks to the same AWS account, these names can come into conflict, potentially slowing down your testing. Prefer using resource references instead.
+-	For things that shouldn't ever be deleted, you can set an explicit DeletionPolicy on the resource that will prevent the resource from being deleted even if the CloudFormation stack itself is deleted. This is useful for anything that can maintain expensive-to-rebuild state, such as DynamoDB tables, and things that are exposed to the outside world, such as API Gateway APIs.
 
 ### CloudFormation Gotchas and Limitations