First, it is important to learn the numbers from 1-10 and then 0-20. Students will be expected to know them forwards and backwards. They will also need to know the number when they see it on its own, without counting. The number words are the next step.
Ways to practice:
Play UNO or other card games where they have to say the number.
Play games with dice where they have to say the number.
When you go for a walk, look at house numbers and read each number aloud.
Count things in your house (forks, pillows, stairs, etc.)
Ask them to turn to a specific page in a book (make it a race!)