In the UK, we use the acronym FAST.
F - Face: If the face is lopsided or the casualty can only smile on one side or if you ask them to stick their tongue straight out it veers off to one side, those are symptoms.
A - Arms: Ask your casualty to lift both arms together, if they can only lift one or one of the arms, once lifted starts to fall again, that's a symptom.
S - Speech: Slurred speech or the use of inappropriate words could also be a symptom.
T - Treatment: If there are any of the above symptoms present then don't hesitate, get immediate hospital help, the faster the better. Whilst waiting for an ambulance, you could help your casualty by lying them on the floor with their head and shoulders raised.