Being a parent for your own children is challenging sometime. But being a step-monther or step-father, I think is a little bit more than challenging. We need a lot of understanding and patient.

I am a mother to my two children and a step-mother for my husband's daughter. I'd like to share some thoughts and experiences regarding being a step-mother.
My husband and I have 4years old son and 1 year old daughter who live with us permanently. My 10 years old step-daughter visits us once a year for 2 weeks since she lives in different state with her mother and step-father. We experienced some different moments when we were all having holidays together. We found that my step-daughter was more interest to spend time with my husband only, which I understood perfectly. We also thought that her interest was a little bit encourage by her mother. We found her always a little bit asked for more attention after she had spoken to her mother on the phone. We also had a couple experiences when her mother gave us a list of foods that my step-daughter could have for breakfast, lunch and dinner. It seem that she didn't believe on my husband nor me.

Since first time I met my step-daughter, I have taken all the chances to know her very slowly. I gave her some space between her and my husband. We did things as family, even so I still felt that I live as a shadow of my husband. Like any other kid, sometime she could be an angel, some time she could be not respectful to us. Sometime she tried to implement the rules from her house to ours which could be different. 

From those experiences my husband and I decided some basic rules, which are:
1. Most of the holiday time, which is family holiday, we try to spend time as much as we could together as family. (This is to create more bonding between me, my children and her).
2. Any decision should be approved both my husband and myself. (This to show that I also have a voice as a step-mother).
3. She has to respect our house rules while she stays with us. (This to show that we don't treat each children differently).
4. My husband will do the talk regarding any disciplinary to her. (I only step in when she's not listen to my husband).

I do not expect much from her or the rules. I understand we don't spend a lot of time too. I take everything very slowly and wish that she could see me as a step-mother that love her as my own daughter.

If anybody had an experience like this, I welcome any other suggestions or comments.

Update:
From last visit, Dec 2005 - Jan 2006, I found to speak less (speak up only when I have to), did the things we both like, offered help when I see she needed one (eventhough she didn't ask, and specially in matter of girl stuff) have created a little connection and respect.