From the Homeschool math Blog, teaching preschoolers numbers.
In a nutshell:
I used foam numbers and plastic numbers, and just made a heap of them between us. I would pick one, hold it up high and call out loud its name, such as "Number five!" and put it to my personal pile.
She would then find the same number (I made sure there were at least two of each) and did the same, called out loud its name and gathered the number to herself.
Then it was her turn to pick any number from the pile, call out its name, and put it to her pile, and I had to find the same number.
After all the numbers in the middle pile were gone, her task was to arrange her numbers in order. That's it.