If a patient who is not in the hospital has possible stroke, the best treatment is to give an anti-platelet agent such as aspirin and anticoagulants like warfarin. This two medication can interfere with the blood's ability to clot and can play an important role in preventing stroke.
Moreover, administering oxygen and initiate transport to the local stroke center is the best thing to do when there is already signs of stroke such as facial droop and paralysis of certain body part.