In my own case it was just over a decade ago when my brother began to sound different on the phone. He lived back East and my parents and I were living on the West coast and in phone calls it became apparent that my brother's voice no longer had the same tones of excitement and humor that he used to; and instead it was very flat. At the same time he began to tell us about a situation at work that just didn't seem possible; he was complaining that a group of fellow workers were conspiring to get him.
My brother was fresh out of college and was starting in a Sales job at a fast growing computer company and said that there was jealousy by the other salespeople there because many of them didn't have a college degree and that he was on the "fast track". Then he started telling us that he wasn't feeling very good and that he thought that one of these scheming co-workers had stuck him with a needle with some unknown drug so as to take him out of competition for the top jobs in the company. He also said he felt strange, and didn't have much energy and couldn't concentrate.
Obviously this whole story seemed very unbelievable and we sensed something was wrong but had no clue as to what it could be. We recommended that my brother quit his job and look for something else - as we began to wonder if he had a "mental breakdown" and would get better once out of the stressful job situation. A month or two after he quit his job he suddenly began calling me from payphones because he thought that people were bugging his phone and that famous business people in the country were trying to get his new business ideas. This was so "far out" as to be entirely unbelieveable and we suddenly realized that something was very clearly and seriously wrong - what exactly that was took us another 5 years to find out definitively, which is the saddest part. We went through a number psychiatrists and psychologists who thought he was fine or only a little paranoid (he always seemed to pull together enough to present a reasonable front to the psychiatrists but we knew the old John, and something was still definitely wrong - but you keep hoping that they are right and that he just needed a few months to get back on his feet).
My recommendation to people who are either wondering if they have schizophrenia or wondering if a friend or loved one has schizophrenia - is to first contact talk with people in the schizophrenia.com discussion areas, or contact the Local NAMI (in the USA), or Schizophrenia Society (in Canada), and visit one of their meetings to talk with other parents or family members and get a recommended psychiatrist from them who is experienced with schizophrenia. I think one of our key problems was that we didn't do this in the early days of my brother's illness (though misdiagnosis sounds very common in schizophrenia cases) - and because of this we may have missed the opportunity to get treatment. This lack of treatment during the early years of the illness, research now suggests, could have been a key factor in his ultimately poor recovery and suicide.
After a few meetings with psychiatrists - and no improvement in my brother's condition - he became disillusioned with the medical profession and would no longer see doctors. It took us almost 6 years until he then degenerated to the state where he could he had become so delusional that he had to be hospitalized. If we had gotten him medication much earlier I think he would still be alive today.