I tutored a little boy who was making very bad grades in spelling. After just a couple of weeks, he was making 100's on all his tests. The school had a list of each week's words so I knew all the words in advance for the next test.
I made flash cards and would hold each word up and make him stare at the word. I would make him use the word in a sentence. We would make up funny sentences and laugh and laugh.
The next day, I would make him write each word 10 times. You could play the memory game and have each word written on two flash cards and play that with him. You could hide the words around the house and make him find them.
Since he is older then have him look each word up in the dictionary and read aloud the definitions. I just tried to make everything as fun as possible and like a game and that seemed to work.