Start familiarizing your baby with the numbers one to ten by rehearsing them with him regularly. Count his fingers and toes or count his soft toys. Start singing nursery rhymes about counting and use your fingers as you sing and count. Popular rhymes include the "one, two, three, four, five, once I caught a fish alive" song and "one, two, buckle my shoe" rhyme.
Add some shapes to your baby's toy box so he can get to know them. Rehearse the name and shape of a square, triangle and circle with the toys and then take him around the house and point at the different shapes in your home together.
Introduce the concept of big and small when you play with your baby. Use his toys to demonstrate the difference in sizes. For example, put a big toy next to small toy and point to each to compare size. You can also use furniture and other people in your home to demonstrate; point to dad and say "big" and then point to baby and say "small."
Show your baby how things can form a pattern or be put in a group. Arrange his toys into small piles according to color, or put the hard toys in one group and soft toys in another. Multi-colored building blocks are a great way to demonstrate this and encourage your baby to join in with you.