Oh dear - my approach might be a little harsh (so feel free to ignore!) but we have a strong willed 2 year old DS and this is how we do it;
Tell him "it's time for tea, you need to sit in your chair" (highchair). If he refuses, no dinner given. Always works (sometimes after a bit of carry-on which I ignore or walk away from) unless he is unwell or doesn't want to eat for some reason. That's it. I have never allowed him the chance to refuse to sit in highchair as I feel he is unable to sit still long enough to eat a meal otherwise. So, if not in his chair, no tea given. We have even reduced snacks in afternoon to ensure he is hungry at tea time and more likely to cooperate. Also, if food/plate is chucked on floor I pick it up without commenting or letting him know this has bothered me in any way and calmly say "Ok, you don't want your dinner tonight" and proceed to wipe hands/face and get him out of chair and remove all food. If they are hungry, they will quickly learn not to throw their food away! I will let him hop back in if this happens and he wants a second chance at eating tea as I know that he is just testing the waters to see what will happen (by chucking it on floor).
GL!