There are four basic requirements for filing a trademark or service mark with the U.S. Patent and Trademark office.*  

1. The trademark application must be based on real intent to use the trademark in commerce, or actual use of the trademark in commerce.  This either means you are actively using the trademark now (actual use), or you have the intent to do so soon (intent to use).  Your “actual use” or “intent to use” is sometimes referred to as the “basis for filing.” 
2. The trademark must be applied for in the name of the owner.  The owner is the person or legal entity that controls the nature and the quality of goods or services rendered under the trademark.
3. The trademark application must specify whether it is an individual or entity that is registering the trademark (i.e. Corporation, partnership, LLC), along with their national citizenship.
4. If applying based on actual use, you must submit a drawing and/or specimen of the trademark used in commerce.  Labels, tags, and containers of the goods with the trademark are some examples of things that are generally considered specimens.  For services, examples include advertising, online websites, and brochures. 

*Other items may be required depending on your particular circumstance or application type.