How do I get my son to listen and not throw a fit while doing what we ask of him

If your son is in the early years before the age of 5 the next time he throws a fit such as laying on the floor scream and kicking do the same thing.. Believe me he will stop immediately in shock of mom acting the same way.. It works I did that once to my son.
Older than 4-5 it is time to use a firm voice without yelling at him that I want this done and I mean now not later.. you must say it with a no argument voice... If he starts to even utter a word about not doing it you say this is not open for discussion.