I've done quite a bit of research about teaching children to read, because we are homeschooling my two daughters who don't read yet, one of which has severe brain damage.
The ideal age to learn to read appears to be between 7 and 9 years of age, which is when children typically teach themselves to read if they have been read to frequently, the same way they taught themselves to talk by being spoken to frequently.
Obviously, children can be taught before they pick it up naturally, and that's not particularly harmful unless it displaces play and exploration types of learning, for which children younger than 7 are much better suited than formal academics.
The first part of learning to read is recognizing that letters have associated sounds: 'A' says "ahh," 'B' says "buh," and so forth.
The second part is called "phonemic awareness," which you can google for a more detailed explanation, but is basically recognizing that words are made up of different sounds. An example of a phonemic awareness test is, "What do you get if you take the 'rrr' off of 'rat?'"
Phonemic awareness is a developmental stage that kids naturally hit around age 3 or 4. You can practice it, but most with most kids you just have to sort of wait until they're ready, and then not worry about it. Kids with reading difficulties often never fully developed in this area, so remedial programs go back to focus on it.
After that point, there is a certain degree of conflict in how to teach reading. The biggest schism at the moment is "whole language" versus phonics. The former is based off the fact that adults don't sound out words, they read the entire word in their head as a pattern. Whole language attempts to develop that skill earlier by focusing on things like lists of sight words. Whole language proponents would say I'm over-simplifying, which I am, but whole language theory is much richer and holistic than the way it usually ends up being implemented.
Phonics is the way you probably learned. You sound out the word and learn the exceptions, then naturally later you start being able to recognize the entire word.
My son was taught for a year in public school on the whole language approach and it did not work well for him. Think of someone reading by looking only at the first two letters of every word and guessing the rest, and you'll have some idea of the result. Again, it may have been a poor implementation of the approach that hindered him, rather than limitations of the approach itself. We switched him to more phonics-based instruction when we started homeschooling him and now he is reading a grade level and a half ahead.
On the other hand, with my 10 year-old daughter with cerebral palsy we work more on sight words, and she doesn't do well with phonics at all.
With my almost five year-old daughter, we take the approach of reading to her a lot, letting her sit in on her siblings' reading lessons if she wants, and basically letting her direct her learning at her own pace. Last week, after I read one of her favorite books to her, she declared she wanted to read it again "all by myself," and proceeded to do so, only needing help for one or two words per sentence.
In other words, every child learns best a little differently, even with the same teacher in the same family. At this point with your son, I would teach him the sounds of the alphabet, continue reading to him a lot, and let him decide when he's ready to go further. There's no rush. Especially if you plan to put him into a public school where he will have to wait for the other students to catch up, the advantages of reading early are relatively short-lived. By age 11, you typically can't tell which kids learned to read earlier than others.
