In the old days, I imagine, looking for high school friends so many years after graduation means getting together physically to pore over the yearbook and call people one after another. Perhaps two people would open their own yearbook and call each other then go over the names and assign them accordingly. Depending on how long back you go, there may be no telephones to use and you would send out copies of a form letter to the last address known for a person. Clacking away on typewriters, running the letter through photocopier, fill out the blank after "Dear", sign the letter then fold it, stuff it into the envelope, and address the envelope. Finally, lick the stamp and affix it then lick the envelope to seal it. What fun!
My recent search for high school friends didn't happen like that at all. We were well into the Information Age, with the Information Superhighway running through our houses, at high speed no less. We didn't have to get together physically. One of us was on the west side of the U.S. and three were in New York City, although different parts of the city and rarely see each other, at least for me. We got on CONFERENCE calls, not one-to-one calls like the days of yore, to discuss things to do and progresses. We actually sent out a few paper letters and they didn't do much good.
One thing we had in common with the old-fashioned approach was the yearbook. Regardless of how the process of finding friends is done, it has to start with the yearbook. However, we had a "copy" of the yearbook in the form of a Google Doc, a spreadsheet, to be exact. It took some time to type in all the names but it was worthwhile. We could sort the list by last name or by first name, or later as we got more info about the students, by other columns, like whether they were on Facebook or indicated they were interested in the reunion. Having all the student names in digital form allowed us to also use the search function to find the names. After 25 years, some of us may remember only the first name of a classmate. By searching for just that first name and coming across all the last names that go with the found first name, perhaps something in our mind would be jolted to come forward.
Besides the yearbook, we also had access to the commencement roster. For some reason, the roster had few or no typos at all so it was a good source to fall back onto. After typing in the names from the yearbook, I also added the names from the roster. An additional bonus with the roster was many of the names had middle initials. If you have to find someone whose first name and last name are common, the middle initial makes a big difference. Yet one other usefulness with the commencement roster is that it may have names of people who somehow were not in the yearbook. Maybe someone transferred into your school after the yearbook photos were taken.
Whether you plan to do the work of finding high school friends with your committee made up of classmates or use professional search service, the yearbook, in digital form (read: searchable), plus the commencement roster if possible, will get you to a great start. It is good to have a pack rat on the committee who can type at decent speed.