how to control my son's behavior?help me

my son is now 28 months.he loves to bang his head to the wall, floor or any hard surface if his wish is not fulfilled. he would also pinch, or spit on us (parent).it’s really have bad impact on us, v r feeling stressed over his behavior.what should v do, not all the time can make him happy.v tried even to switch to any other topic and make him forget of what he is wanting for but all the efforts is just helpless.

Can you give some specific examples of what sets him off?