In order to be proficient readers, children need to know a number of things about how print works in the English language. These include the idea that:
Print has meaning
Print can be used for different purposes
Text in English is read from left to right and top to bottom
When you get to the end of a line you return sweep back to the beginning of the next line
There is a difference between letters and words
There is a difference between words and sentences
Where you start reading a book
Words are separated by spaces
Punctuation marks signal the end of a sentence
Books have front and back covers, title page, and a spine
Once a child has developed an understanding of these concepts, you do not need to keep teaching them - they are fairly straightforward concepts that are continually reinforced as children continue to develop as readers and writers.
Download this comprehensive Concepts of Print Assessment, originally designed as part of the Michigan Literacy Progress Profile.