How to discipline my 8 yr old daughter

I'm a married woman with 2 kids. My eldest is 8 yrs old and my youngest is 1year and 9 months old.
These kids are with different father, i got married with the father of my youngest daughter. My eldest daughter is living with us. It is very difficult to discipline her. I think she's getting stubborn, she's getting lazy. I always mad and nag with her most of the day after my worked. She was not able to listen with me and with her grandmother.
Sometimes i want to spank her but i know she will not stop crying, she cried and cried. And i'm getting embarassed with my neighbor.
Pls. help me to discipline my daughter.
What is the best thing to do to discipline her.

[AnnieBrooke]

You might see if you can get a copy of "How to Talk So Children Will Listen and Listen So Children Will Talk."  It's paperback and very inexpensive on Amazon, and has a great easy style and is useful as heck.  Probably the best book on discipline and communication with  kids that I have ever seen.