I have been a woman owned business for many years and have just been told I
should register as a minority vendor. However, no one has told me how to do
that. Is it by State or county or what?

Once you've established your business, you may also want to look into the major certification bodies.  The one with which I'm most familiar is WBENC (Women's Business Enterprise National Council).  While there are very few set-asides or priorities for women owned businesses at this time, most large corporations require a nationally recognized certification such as WBENC to qualify for any woman-owned business advantages.  It's not free, but relatively inexpensive to apply.  It's renewable yearly.

Another thought - there are often local groups focused on assisting women-owned or minority-owned businesses.  In the Phoenix area, for example, there's an organization called the Grand Canyon Minority Supplier Diversity Council.  They work with small businesses (vendors) and big companies (buyers) to increase procurement through minority-owned businesses.  That organization has their own validation process, if you will, to become a member.  It's completely separate from 8(a) and any other minority-owned certification.  So you may want to look into that for your area as well.

Like bizresearcher said, your first step is to register like any other business, then apply for __-owned status.  However, you can be registered as a woman-owned or minority-owned business for more than just federal contracting.   Your local governments - state, county, and city - also do a lot of purchasing.  Many of them will also have programs to promote purchasing through woman-owned and minority-owned companies.  To qualify as one, you will need to find out each entity's requirements and go through the application for each program.  This means that you may have to register for city, county, state AND federal programs.  Depending on what your business does, these local governments may actually be a better fit for your business.   Many municipalities have departments specifically to help small businesses, which will include services to educate and assist you through the application process.  Your state's department of commerce or your local SBA office can direct you to these resources.   Hope that helps!

Before doing anything, first understand the difference between the terms: women owned business and minority owned. If 51% shares of a company are owned by women, or have fewer shares but are managed and controlled by women then it's called a women-owned business.' For getting comprehensive details and guides I suggest you visit http://www.womenbiz.gov/resources.html. This helps you to find all the answers you need like tax filing, certifications, financing, training and technical assistance etc. Moreover, government contracts can be a great source of business revenue for both new and established businesses as the federal government does not require certification for women-owned small businesses. But to get these contracts, you have to understand the process and how to navigate it successfully.

Being a woman and/or minority-owned business is relevant only when contracting with the federal government and possibly your state government. You register your business name and entity type with your state or local agency just like any other business. If you provide a product or service that may be useful to the federal government, then you would obtain 8(a) status through the Small Business Administation. You can find information on the SBA web site.