Well, that was a funny and interesting game! It took me several attempts and playtests for me to find out which guests I should invite and which ones I shouldn't. I think these are the people you should and shouldn't invite:
Invite: Postman, DJ
50/50: Random passerby, friend from high school and college
Don't invite: People who won't tell you their names
Other: People who wants to know what time it is.
I'll admit some of the dialogue made me go O_O when I realized that I accidentally let in a killer. For example, when I let in a random passerby who was actually disguised as a murderer, they said "my name is (name), and you will remember it!" And when I let in a killer who claimed to be your old friend, they said "friends forrrrrrrrever!"