There are three types of trademark symbols, each one has a different use and different rules regarding when and what it may be applied to. Two of them may be used while your trademark is pending.
The “™” designation is used to let other companies know you consider something trademarked, have an application pending or have a common law trademark. You may use it anytime. However, it does not guarantee legal rights. It may be used to determine or establish some legal rights but it doesn’t automatically grant you any.
The “SM” designation is used similar to the ™ designation but is used for service oriented businesses. If your company focuses on the delivery of services you may want to use the “SM” until your trademark application is approved.
The Circle R designation is only for trademarks that have been approved and registered with the USPTO. Once your application is approved you will receive a certificate from the USPTO that will allow you to use the Circle R. If you use the Circle R without permission you may subject yourself to false advertising or unfair competition claims.