Are there any specific forms to file - in order to qualify the DBA and to provide the legal status of the DBA ?

You asked this under Corporate Law, but are you a sole proprieter, using your own name and SSN and a DBA business name? If so, generally there is nothing you need to do. Some states have laws about uses of certain words not being allowed. You can check on your state.gov website. I wouldn't worry about it too much if you are new and just starting out.

Check with your local licensing Dept. Some require an "alias " form outlining the name. John Doe DBA JD services for example.

Each state has different procedures for this. You do know there are 50 of them, right?

It depends on what you want to do with it. For example, my bank required me to register as a DBA with the county (NYS) before it would open a bank account in the business name so I could deposit checks made out to the business.

A sole proprietor, or in theory another business entity (such as a corporation, partnership, or LLC) can be "doing business as" some trade-name. I, for example, sometimes do "business" as "AK Lawyer, the sarcastic". (as in my previous post).

But my point was that a question for "specific forms" cannot be answered without knowing the specific jurisdiction. While the federal government does regulate an ever-increasing portion of our society, the regulation of the circumstances under which one may use a fictitous name for business purposes is still under state (or perhaps local) perview. Also, you might want to reserve a fictitious name so as to prevent others from using the same name. There are optional procedures for doing that in many places. You should also as a precaution check to see that someone else has not beat you to it, and has already reserved the name.