It can be very important to check someone's criminal background if you are working with them or becoming involved with them.  It can be especially important to conduct a free criminal background check for people who work with your children.  And you have been trying to search online how to conduct a background check.  If you come across some ads that offers free background check, most probably it is a free preliminary search.  It is not free as it will ask you to pay a certain valuable amount to check their records which may possibly be in detail and better than the details that they can offer you for free.  So if you are short of time, it may be a better deal to pay for a background check rather that conducts a free background check.  But if you think you have the time, then by all mean, do it yourself.  If you know the person, then all you need to do is conduct a web search on their name using different search engines like Google or Yahoo.  Social networking sites like Facebook, MySpace among others are proven to be helpful where you will find their details such as their date of birth and phone number.  In case you cannot find it, the strategy for you is to get a little friendlier with the person that you want to conduct a background check, and ask them their date of birth.  If they ask you why you are asking them, tell them that you want to mark their birthday on your calendar.