I usually look at the color of fruits, then see if they are hard or soft to touch. If they are soft, they are not going home with me. If they are too hard, then they are not going home with me either. I don't want to break my teeth trying to chew a super hard apple.
As for fish, I try to find fresh fish. Usually the seafood sales associate knows if it is fresh or frozen, so I always try to ask if someone is around. If the store doesn't have fresh fish, but frozen fish, I usually take it home, thaw it a bit and then cook it so that it tastes more fresh.
As for meat, I look at the expiration dates on packages of meat. If I know that I will be cooking the meat within a few days, I will get the meat that will expire in 3-4 days. If I am not sure when I will be cooking the meat, I will usually get the meat that will not expire before 7 days. Also, for meat, I usually try to look for color. I don't like blood in the meat pan (personal preference), so try to find ones without visible blood.
This was a great question!