Well people could stop polluting his kingdom and killing his subjects for a start.
Okay, anyway the way the ancients Greeks used to honor the Gods was by burning food in a brazier in their name or sacrificing an animal to them, usally a goat or boar or something similar.
To honor him, of course!
gives him the insides of cows
yes
To attend a banquet in his honor.
Yes
they had religious festivals for him and built temples
No, apollo did
the function of Poseidons temple was for Poseidons honor.
Because since he ruled the seas they hoped it would help the fishing
Poseidon himself lived under the sea, but the Greeks built several temples in his honor. Some are: in Paestum (southern Italy),Greek island of Poros, Cape Sounion near Athens, city of Corinth, and others.
He had a strong sense of Honor He never broke his word, and unlike Poseidon and Zeus, He never cheated on his wife.
He made the first horse. He also gives good weather to sailors who honor him.