I know that you can set Security Group rules with
ec2-revoke. How do you view the rules of a given security group?
All commands available within the Amazon EC2 API Tools are documented in the Amazon EC2 Command Line Reference - informational commands usually follow the ec2-describe-* pattern, and the one you are looking for is ec2-describe-group:
will show the list of all security groups
to get only security groups names
to get the policies for that sec group