A federal trademark needs to be filed with the USPTO, in Alexandria, VA. Once a trademark is registered with federal government it means nobody else in the United States can use it or something similar if it will create a likelihood of confusion. Most intellectual properties attorneys can file your federal trademark. In addition to greater protection, a federal trademark, also only has to be renewed every 10 years. A state trademark has to be renewed every 5 years.
A state trademark is filed with the individual state office. Your state trademark is only good for the state you live in and does not provide you protection in any of the other states. For businesses that only want to stay in one state and not expand a state trademark may be ok. However, most businesses will expand at some point in the future or attract numerous clients from out of state. If you do choose to only go with a state trademark application, you should contact attorneys who are licensed to practice in your state.