A criminal background search is the process of finding the criminal history of an individual. Criminal background checks are routinely performed before employment is offered, with an offer of employment being conditional upon a clear criminal record. A person's arrest history, incarceration records, and instances of sexual offenses can be found through the performance of criminal background searches.
There is a big difference between a “Criminal Records Search” and a “Criminal Background Check”. A “Criminal Records Search” is searching a single database with the identifying information that you have been provided. A “Criminal Background Check”, on the other hand, will discover and verify your subject’s personal information, thereby establishing positive identity, plus searching a variety of databases.
Criminals are experts at supplying you with bogus information. They use aliases and variations of their name, change around or alter their date of birth, change their social security number, and leave out past addresses?
HOW TO CONDUCT A BASIC BACKGROUND CHECK
STEP 1 – GATHER INFORMATION – POSITIVE ID
The first goal of any background check is to obtain a positive identification of the subject in question. The important preliminary information needed includes full name, date of birth, social security number and a current or past address.
Date of birth is a very important identifier and necessary to search criminal records.
STEP 2- CONFIRM – ADDRESS HISTORY SEARCH
- Address History w/Phone Numbers
- Age/Date of Birth
- Alias/Maiden Names
- Neighbors
- Relatives/Roommates living at same address
- Dates of Residence
STEP 3 – GENERAL RECORDS SEARCHES
Search Vital Records, include births, marriages, divorces and deaths - all of which are public record. Financial Searches often indicate financial standing and responsibility.
STEP 4 -- CRIMINAL RECORDS SEARCHES

• Local and County Checks
• Statewide Criminal Courts

Source1: http://www.zimbio.com/Criminal+Background+Check/articles?Page=8
Source2: http://howtoinvestigate.com/articles/free-criminal-records.html
Source3: http://howtoinvestigate.com/articles/basic_background_check.htm