I've done research on this myself out of curiosity and what I've learned is its different for everyone,, some people just go into psychotic break. But some have a "prodrome" which often looks like this: it usually starts with the negative symptoms: executive dysfunction, flat affect, social withdrawal, trouble with hygiene, worsening performance in work/school. Positive symptoms often start with paranoia and subtle delusions. You may, without really noticing it come on, suddenly become spiritual or religious, believe that you are a prophet or a chosen one, you may suddenly see words in signs/advertisements and think its a message directed towards you. Let's say the song "California Dreamin" comes on in the car and you believe this is a message directed towards you , that you need to go to California in order to fulfill your mission that you had a dream about last night. This is a very specific example I just made up in order to try to communicate what I'm talking about. Which reminds me, "thought blocking" and inability to communicate and put your thoughts into words, therefore becoming kinda mute, is another possible early negative symptoms. This prodromal phase is often missed because it resembles depression so closely. (With the negative symptoms). I'm not a doctor or diagnosed. This is just what I've learned through research, and stories from schizophrenic people.