8 month old throwing fits! Help!?

My 8 month old son has been throwing fits and I'm not sure what to do. He is only 8 months so there is a lot of things he does not understand but he knows he is throwing a fit. If he does not want to be in his high chair he will just scream and scream. He hates getting dressed. If I don't let him near things that he wants to check out (like the dog dish or the fireplace.) he gets really mad. Don't get me wrong he is not like this all the time. He is a blessing and I love him so much. But what do I do? Please help moms! :)