You should follow the below practices in using the tags

• Inform each team and stakeholders about the right tags so that they can use them and check periodically for the same in reports.
• Use tags consistently
• Tag owners should be identified to enable use and tracking of tags
• Tags for cost
  1. Tagging decisions are reversible, giving you the flexibility to edit or change as needed in the future. However, there is one exception—cost allocation tags—which are included in AWS monthly cost allocation reports. The data for these reports is based on AWS services utilization and captured monthly. As a result, when you introduce a new cost allocation tag it takes effect starting from that point in time. The new tag will not apply to past cost allocation reports
  2. Adopt a standardized approach uses the naming convention as listed in the document below for resource specific tags
• Tag everything
• Constrain tag values: Tags are not useful if they contain missing or invalid data values. If tag values are set by automation, then automation code can be reviewed, tested, and enhanced to ensure that valid tag values are used. When tags are entered manually, there is the opportunity for human error. Reduce this by using AWS Service Catalog
• Propagate tags and then tag values across related resources
• If tags are used in access control limit, users have the ability to modify tag values in order to gain access
• Use AWS Configuration to create rules to check resources for required tags as it will continuously monitor your resources against those rules 
• Impact analysis, approval, and implementation for requests to add, change, or deprecate tags application of existing tagging requirements as new AWS services are adopted by monitoring and remediation of missing or incorrect tags

• Use each key only once for each resource. If you attempt to use the same key twice on the same resource, then your request will be rejected.
• You cannot tag a resource at the same time you create it. Tagging requires a separate action after the resource is created.
• You cannot backdate the application of a tag.
• Maximum number of tags per resource: 10
• The more tags you have, the better your AWS visibility.
• Standardize your tagging format to prevent duplications, mix-ups, and inconsistencies.
• Don’t use tags to store confidential data such as your personal information. Because tags are used across many services on AWS, the information could be accidentally shared
• Automation tools, such as CloudFormation templates can help you tag resources proactively, especially as you scale.
• Get notified automatically when tags are incorrect or missing.
• Designate a tag owner – the individual who owns a specific tag and can demonstrate its value to the organization.