Following the addition of tags, AWS Cost Explorer is not displaying accurate billing information. Please provide best practices for effective tagging.

Can you provide an example of the problem you are facing. What wasn't accurate in your exercise?

Here are the best practices as published by AWS: https://docs.aws.amazon.com/whitepapers/latest/tagging-best-practices/cost-allocation-tags.html

If you are using the user-defined tags to your resources. Note that it can take up to 24 hours for the tag keys to appear on your cost allocation tags page for activation. It can then take up to another 24 hours for tag keys to activate. AWS generated cost allocation tags can take 24 hours for tags to activate.

However if you are referring to AWS Organizations resources tags, unfortunately Cost Explorer does not support these tags yet.

It would be good to understand what the inaccuracies of your billing information in cost explorer are to understand which best practices to follow.