One of the first decisions in beginning a search is to decide who will do the searching. The choices include:

Conducting the search on your own:
For some, it is an important journey to go through the search process. It can be exciting and healthy to feel in control and a part of the process by being very personally involved in your own search. Many people search on their own to keep the costs down as well. Probably the chief disadvantage in searching on your own is that unless you proceed in a very orderly, methodical fashion, and are educated about searching, your search may consume a great deal of time and energy.

Using a professional adoption searcher:
This might be a better option for someone who simply wants to get it done in a short amount of time. Probably the biggest disadvantage is that using a professional searcher might be costly.

Choosing a private investigator to conduct your search:
This method is similar to using an adoption searcher, as far as costs and time factors. However, a private investigator may not offer understand the dynamics of adoption search as well as a professional adoption searcher.

Using search angels or knowledgeable volunteers to search for you:
This method could be somewhat hit or miss depending on the skill and the available time of volunteers. I could also take a great deal of time;

Having a agency conduct a search for you if your state allows them to:
If the state in which your adoption occurred in allows agency searches, this could be a reasonable alternative. The disadvantage to agency searches are the expense and the backlog that many agencies may have. Searches conducted by agencies may proceed somewhat slowly. It depends greatly on the agency.

Hiring a private Confidentiary Intermediary ("CI") to conduct your search (again, only some states allow Confidentiary Intermediaries):
The advantage of a CI is that they will have access to your adoption file that you may not have. Therefore, the chance of finding your birth family member is fairly good. The cost of using a CI. is a factor to consider. Another disadvantage to using a CI is that they must make the initial contact. If the found party does not wish contact, they close your file and you do not receive contact or identifying info

(SEE "Using an Intermediary - Two Stories")

Any combination of the above.
However, I believe if you hire an Confidentiary Intermediary to search on your behalf, you may have to sign an agreement to not search on your own while they are searching for you. Beginning a search on your own and then seeking further help when needed could make a great deal of sense.

As you can see, there is a wide variety of ways to conduct an adoption search; each has advantages and disadvantages.