If you were born in the U.S. and want a copy of your birth certificate, the process is straightforward. Birth, death and marriage records are kept on file with county and state agencies and while access laws vary, in general, you apply to the appropriate office with photo identification, pay a modest fee and wait until it either arrives by mail or is ready for pickup. However, the process becomes more complicated if you want to find birth records of relatives, ancestors or people unrelated to you. Hundreds of for-profit companies are eager to accept your money for research you can do yourself.
Research applicable state and local laws. Laws and policies vary widely from one state to the next. For example, anyone can go online and get the birth dates of people born in California from 1905 to 1995 through the California Birth Index, but most other states treat such records as highly confidential. Some states permit public access to old birth records but safeguard the privacy of more recent ones. Type into a search line the name of the state or county, "vital records" and "access" to find out relevant policies and procedures. The Centers for Disease Control also maintains a website giving detailed information, organized alphabetically by state, about acquiring vital records.
Compile as much information as possible. Full name, including middle initial, of the person whose records you seek, place of residence, year of birth or death, and the names of parents all help to narrow down the search. Some sites allow you to search free but demand a subscription fee if you want to see the results, meaning you can't know how much (or little) useful information exists until after you've committed yourself.
Search online or through library public archives for burial records. If your priority is information rather than documentation, burial records and inscriptions on cemetery tombstones often yield as much or more as birth records. Type "burial records" and the name of your state or county into a search engine to learn what's available. The website of the U.S. GenWeb Project, a group of volunteers working to keep Internet genealogy both free and comprehensive across every state and county in the U.S., is also an excellent resource.