I was trying to figure out how find my adopted sister she was given up for adoption in 1989.my question how do I go about finding her and will it cost any money and how much and who do I need to contact to find her?

1. You ask your shared parent about her.
2. You hire a private detective---VERY costly.
3. You post on reunion websites such as adoption.org, adoption.com and ISSR.

YOU have no right to leave messages for her at the courthouse or at the adoption agency. 1989 is a borderline year--open adoptions were just starting to become common then. Your sister may not KNOW she is adopted.

Why do you want to know so badly, anyway?

Depends on what state you are in and what information you have gathered.
Do you know her exact birth date? Do you know what state and county she was born? Do you know what agency if any handled the adoption?

Some states if you contact the agency (you may have to be the parent to do this) and fill out the request forms they will send you Non identifying info and then they will contact the adoptee and ask if they wish to have their contact info shared if the adoptee states yes they will then give her your contact and vice versa.
That is basically how the registries work as well. They will contact you both and match info as much as they can and if both parties are in agreement they will give the info to you both to make contact.

As the person above stated though there are MANY reunion registries out here and they do work. I placed a child for adoption when I was 16 and thanks to a online registry I was reunited with her 12 years ago. So they do work.
Just do a Google search for adoption registries
Make sure you know also that there are sadly scammers out there so read some of the warnings on the sites to stay safe.

There is a list of registries here
Adoption Reunion Registries - Find a Registry Adoptee. Adoptions

Sunflower Birthmom Support Group for women who relinquished a child for adoption

Another good list of resources

Helpful Sites

There are LOTS more

There also are some Yahoo groups dedicated to searching and there are message boards that are there to help and share info
Adoption Forums, Message Boards, Discussion Groups. Adopting, Foster, Baby Adoptions

Good Luck

You DO need to either be the adoptee, the adoptive parent (for a minor child) or the birthparent for ANY information to be given to you by the courthouse or adoption agency. I have yet to hear of a single state that varies from this.

The ONLY reason a closed adoption will be opened by the courts is for a medical emergency.

A sibling has NO RIGHTS to information regarding a child that has been adopted. You might get lucky on a reunion site, and you may be able to find your sibling with a private detective---but you're going to get absolutely nowhere if you don't have the cooperation of the birthparent involved to get more information.