How can I tell if the beef is fully cooked?

I don't know how to cook beef.So i can not pass the comment on it.

First: Define fully cooked? (lets say plus 75 degrees C!)

Use a probe thermometer inserted to the point furthers from any heat (deepest).  

Or if not thermometer is available insert a stainless steel larding needle or skewer to the deepest part for a few seconds - pull it out and test on back of your hand - should feel hot if cooked - not luke warm. Always look for clear running juices and no traces of blood

its depend on the beef meat part. and i"m agree with mr ronaldo no more blood dripping and when you press is hard. you will notice it while you grill any meat.