The symptoms of a heart attack or seizure are pretty easy to identify and therefore it's easy to tell what kind of help the victim needs to survive, but when someone's having a stroke it's really hard to diagnose and even harder to treat.
So according to this TED talk by Vaibhav Goswami it's important to "Act F.A.S.T.", identifying whether they have Facial drooping, Arm weakness or Slurred speech, then acting fast to get them to the hospital in Time.