I taught basic phonetics and blends (e.g. th, sh), vowel sounds, and short sight words. The sight words were the most helpful. He independently read his first book just after his fifth birthday and was reading chapter books within six months.
I want to add that I felt DS was "ready" to read, was deeply frustrated that he wasn't reading, and needed only very basic instruction to get him there. I've seen several of DS's friends learn to read a year or two later (generally around mid first grade), and catch on quickly.
