General consensus states that most people regard Professor Sybill Trelawney a mockery of a Divination teacher. It appears that most of the time, Trelawney reads too much into superstitions and can create a tragically dramatic prediction from a sneeze.
Even Hermione walked out of her class and considered it a waste of time, something we all thought Hermione would NEVER do.
It turns out that Ron and Harry, who usually spend a majority of that class goofing off and joking about how silly and useless the subject is, might actually be a lot better at reading crystal balls and tea leaves than they give themselves credit for.
Rowling, you cheeky lady, you! Dropping hints left and right, and we didn't even notice them until years and years later. She is one smart cookie.
And perhaps Harry and Ron need to accept the fact that they might possess the Inner Eye. Sure, Trelawney can make big predictions, such as when she predicted Harry's prophecy. But perhaps Ron and Harry know more of the day-to-day occurrences.