Blocking in a fist fight?

stay out of their range. get in strike and get out.... when facing multiple opponents the best thing you can do is run because it's just a simple fact when fighting more than one person your odds of winning are very low. but if you are unable to escape, corner your self up into a wall and start swinging. or keep all of the attackers in front of you. if they are all in front of you turn and run. By having them in front of you you can see them coming, if your surrounded you can't see what's coming. But as far as blocking, simply stay out of their reach/range, parry punches, learn trapping techniques, block with your elbows, and forearms. hope this helps.