It doesn't take much to turn every day experiences into a wealth of learning for a youngster just starting out on his or her learning journey. Counting plates or cups while setting the table can be a great way practice counting skills. Asking questions like, "We put out a cup for your sister and your mom, how many more do we need?" can help with early addition and subtraction skills as well. If a child doesn't know the answer to the question, maybe say something like, "Hmmm. What can we do to figure that out? Ah! What do you think about counting the places at the table that have plates, but don't have cups?"
One can help children learn colors by using the color names in everyday speech. Saying things like, "Oh, look at the blue car" or asking, "Would you like to wear this green shirt or that yellow shirt?" are great ways to "teach" colors.
Some of us have experienced a child asking a mountain of questions. Every time you turn around it is, "why is this…, or how do you…, or what is this... or why is that… ." Sometimes those questions come at the most inopportune times too. But, don't squelch the questioning. Encourage it! And, not only encourage the questioning, but model it. Questioning is a great way to learn and facilitate the awe of learning.
Learning letters and letter sounds can be practiced by saying things like, "Look at the McDonald's sign. That looks like a great big M!" Something like, "Will you please go get me some Kool-aid? What is that first letter you will be looking for again? Oh, yes, I know. It is a K!" would also be effective. Or, something like, "Hmmm. Ball starts with a /b/ sound. (Maybe pretend to dribble a ball and say the /b/ sound every time you pretend to dribble.) What else starts with a /b/ sound?" is wonderful for beginning sound practice.
Yet, making these things a sit down discussion is not preferred and unnecessary. Have these discussions as part of your every day activity. The knowledge will be more apt to be integrated and enjoyable if the teaching is more integrated and enjoyable.