DebbieHep beat me to it! I agree that you should use the alphabetic code with your child. Here are my suggestions:
Phonics
First, look carefully at the words and identify the letter-sound correspondences. Try to say the sounds and point at the letters, rather than say the letter names, as letter names can be confusing when talking about the sounds.
? Some key words are straightforward, e.g. ?big?: ?b...i...g?. For those words, ask your child to say the sounds and blend them every time he forgets them.
? With words like ?out?, ?then?, ?look?, ?back?, make sure he knows that ?ou?, ?th?, ?oo?, ?ck? are each code for one sound (although they are spelled with two letters).
? Words like ?me? and ?go? are only a little tricky. Just explain that in these words ?e? is code for ?ee? and ?o? is code for ?oa?. (I mean the sound made by the letters ?ee? and ?oa?, but I wouldn?t say it like that to a child. It?s much easier to talk about than to write down in this message!)
? Other words are more tricky. With a word like ?come?, say the word carefully together ?come ... c...u...m? and notice that the ?c? and the ?m? are letters you?d expect in the word, but the ?o? and the ?e? are tricky.
With ?where?, say, sometimes this (pointing at ?wh?) is code for /w/ (unless you?re Scottish) and this (pointing at ?ere?) is ?air?.
Do you get the idea? It means he won?t have to remember the whole word like a picture. He?ll only have to remember the tricky parts, and analysing the words will help him remember. Let him read them like this several times if he needs to, before worrying about whether he remembers or not.
Timing
However, some children have much more difficulty than others in moving on from here to saying the words automatically. If he isn?t remembering a word after you?ve done this more than five or six times, you could try timing him, but only after you've talked about the sounds. Time him reading all the words he brings home and write down how long he takes. Let him take as long as he needs to work out the words with your help, as above. Later or the next day, ask him to read them again. Repeat this several times. There may be a time when he takes longer than a previous time, but overall, he will get faster and more automatic. If he?s competitive, he?ll enjoy beating his previous time.
A game
Talk about the sounds as I said at first, before playing this game. Write the words on cards, with two cards for each word. Play pairs. Turn them all upside down on a table and take turns picking two. If you get a pair, you keep it and get another turn. You have to read the words before you can keep a pair, but it's okay to read them slowly, sounding and blending. I find children usually win, because they?re better than me at remembering the position of the words.