You may find that there are some words which cannot be sounded out using phonics rules (eg ‘one’) or which, by itself, cannot be easily explained to a child (eg ‘is’, ‘to”). Such words form part of the ‘Sight Words’ list or commonly known as the ‘Dolch Word List’ and mastering them may enable a child to read more efficiently as the words in the list is said to make up 50-75% of all words used in books.
An example of the Dolch Word List can be found in this website.
Here is what I did with my then-5yr-old boy:
While the website split the word list into 3 sets, when I first introduced my elder boy to sight words, I split up the 220 words into sets of 10 words.
Paste/magnet the slip of paper on the fridge and go through it twice a day.
Replace the set with a fresh one when the boy has cleared all the words in the set.
Revise the previous sets once the boy has cleared the current set (eg when the boy had cleared Set 5, do a quick revision from Set 1-4 and so on).
It is prudent to note that while the child may be able to read sentences after he/she has mastered the sight word list, it will take reading practices for the child to be able to understand what he/she has read.