Put some objects in a line and get your child to count them. These can be pens, cars, tins etc. Start with a few objects and gradually increase the number. You can then get your child to start from the other end and go backwards.
Ensure that they say 1 number name for each object.
If they count too fast or too slow, spread the objects far apart-but still in a line-so that hey have to move to each object to count them.
Once they have got to the end-ask them how many objects there are-can they tell you without having to re-count them?