Monitoring your trademark sounds simple, but you would be surprised how many trademarks are just sitting there with no one paying attention to them. Once your trademark registration is approved, you can start using the registered trademark symbol, ®. But your efforts to protect your trademark shouldn't end there. Throughout the life of the registration, you must police and enforce your rights. The USPTO registers trademarks, but it does not enforce them – that's up to you.
One way to protect your trademark is to monitor USPTO filings and oppose any applications to register trademarks that seem similar to yours. Another is to be assertive if you learn that another company is using a name or logo that’s similar to your trademark. Sometimes, a letter to the infringer will stop his actions. However, if that doesn’t work, your federal trademark registration gives you the right to file a lawsuit.