Start with YOU. Who is your dad? Who is your mom?
Your dad had a mom and dad. Who are they?
Your mom had parents too. Who are they?
Each of these people had parents. Each female (usually) had a maiden name. That's the name she got from HER father and will help you search the females of the family. When you get stuck, Google names. You'll get it. or come here and ask for help again. Through a name out you're stuck on and we'll try to help.
Good luck and have fun with it. You might learn all kinds of secrets etc. It can be exciting!

what happens when you dont know mothers parents and she was adopted

If someone has been adopted - get in touch with the Salvation Army or Social Services for the area where the individual came from.
Records are available for births marriages & death on Ancestry.com or Find my Past.
If you subscribe to a worldwide subscription it allows you to trace other members of your family who might have emigrated
Good luck with your research any ? you can find me at Rickarby roots

Here's some pages directly addressing adoption and genealogy. Hope these help!--treenut

http://www.genealogy.com/69_taylor.html All About Adoption Research
http://rwguide.rootsweb.ancestry.com/lesson31.htm RootsWeb's Guide to Tracing Family Trees
http://www.findmypast.com/content/adoption-records-and-genealogy Adoption records and genealogy