First, I got a cute notebook on clearance at Target.
Then I wrote in the whole alphabet in big, bold letters. Both lower and uppercase.
I also wrote in some simple 3 letter words.
When we were first starting out I would work on it with him a few times throughout the day. Just a few minutes here and there. I wanted to teach him both the uppercase and lower case, and the sound of each letter. If he couldn't answer, I would give him the answer and we would move on to the next.
He now knows all the letter sounds, and can tell you a word or two that starts with that letter!
Here is a video to show you his skills. It's a bit long, but it's pretty stinkin' cute. Aaand he breaks out in song in the end, so you'll be glad you stuck with it.
The next thing I want to work on with him is learning to write his name!