Matching a picture with the sight word will help reinforce the word and its meaning by giving a child a visual cue he can call up when he sees the word in print. For example, you might want to focus on words with a short "a" sound, so on flash cards or a bulletin board, present the following words with pictures to match: can, bat, rat, mat, man, hat, ram, fan, and cat.
Some children and others learning to read are more likely to learn new words by hearing them spoken aloud and then repeating them while looking at the words. These auditory learners will also learn basic phonics if they say the words as they write them or as they come to them in print. This is one of the reasons why poems or just a series of rhyming words can be especially effective in helping beginning readers master sight words; similar-looking words are often similar-sounding words, too.
All subjects have a certain vocabulary and frequently used words. Content sight words in science, for example, may be much longer or more complicated than basic three-letter sight words. But because the words appear often in academic texts, these words should be instantly processed. If the subject area is natural science, for example, words such as "species" and "adapt" should become sight words for science students.
If you are content area teacher, such as social studies or science, compose a list of content sight words for each unit you cover with your students and put them around the room if possible, or at least in a visible place on bulletin board. Some of these words may be unfamiliar to students at first, but if you go over definitions of the words at the start of the unit and then at the start of each class point to a random word or two and ask for definitions, the students will become more comfortable with them. Soon, what might have been words that tripped them up will become content sight words that will help them master the subject faster, because they aren't having to struggle with the basic vocabulary.