Its not hard to feed a fish isn't it? But dun expect they take whatever we throw at them! I think the first principal is need to know type of the fish, is it herbivorous or omnivorous or carnivorous? For my case the herbivorous should be the easiest to feed. At least can be feed using nori sheet. But most of us will prefer the fishes take the pallet food. Yeah its a lot easier, we can simply put in food timer and just needed minimal time to check if empty.

Most of the time if the fish refused to take food offered because of stress or loss appetite. In this case i always separate them in a net or whatever before put them in a main tank. Normally i just release after they have taken food offered for sometimes. 

Anyway there is a guideline how to feed finicky fish. Please refer to this site OR this site about that. Other than that just try with a proper size of pallet (this might be the goal) with several brands of pallet and mix it with frozen food.