I think it's whatever the child likes to learn with. When DD5 was 18 months she loved to count everything I used flashcards to get her started (around 12 months) but she would count whatever she could get ahold of. One of her favorite things was counting her diapers. We have a big house so I would have them stashed in different spots so I wouldn't have to run around and find some. She would gather them all up and count and arrange them in a half circle, even at this age she could count to 100, when DD4 was born (their 19 months apart) she had little diapers to add to the half circle. She did this with crayons too. DD4 doen't like the flashcards at all she learned to count by me reading counting books over and over, finger and toe counting a chart we have up to 100. So I think every child learns different ways.
