There are simple understandable method to identify stroke. STR (Smile, Talk, Raise hands).
Smile
Ask him/her to smile. If s/he kan smile properly, then most probably s/he is not getting stroke. But if s/he's smiling and the smile is not symmetric, up or down on the left/right side, you should pay more attention and might suspicious of it.
Talk
Ask her/him to talk some simple words. such "I can see". "I love you" etc
Raise Hands
Ask her/him to raise her/his hands.
If the patient can't do one of those three. Go call an ambulance and explain the condition to the nurse.
This is just a simple method, but it might be useful for you someday if the worst thing happened to the people around you.
Additional Method: Ask the person to stick out its tongue. If the tongue is crooked, or if the tongue is lolled to one side or another, these are signs of a stroke.