People often ask me what I do to teach my sons. My usual answer is "nothing, I don't teach my sons". Yes, now the do workbooks every day, but that really is more of a review. Blake is learning a few new skills through them, but it is stuff he has already taught himself in a lot of ways.
But, the thing I don't always say is there are so many moment in the day that can be turned into a learning moment. I'm always talking to the boys about letters, numbers, colors, shapes, science concepts and so much more.
If you stop and think about your day, there is so much learning that can easily be incorporated into what you do. If your child asks for something to eat, have him tell you what the food is and what sound it begins with. We often then jump off to other words that begin with the same sound. Colby: "Mommy can I have popcorn please" "Sure, what sound does popcorn begin with?" "/p/" That's right, what else starts with the /p/ sound?"
When playing with toys, have them count the object they have decided to play with. If you take away 1 how many do you have now? If you got one more how many would you have?
If your child draws a picture, ask him to describe the picture to you. Then write what he says on the page. Then read it back to him. This allows him to see that his words and the words on the page match.
As I've said many times, getting kids into the kitchen is a great way to teach math and science concepts too.
I do most of these things without even thinking about it now. Try to get in the habit of making every situation one where some learning can occur.