Let your child use your fingers to open up one at a time counting to 10, once they get to 10 give them a big tickle! You could then use their fingers and they get to tickle you. When they are comfortable with counting to ten you can start with your fingers open and they count backwards putting one finger down at a time. If they master counting to 10 use your hands and theirs to count to 20 before getting a big tickle.