Use a developmental screen such as the LookSee Checklist (formerly NDDS). It is a quick checklist that will help you determine if there are any areas in your child's development that may require extra help.
The checklist includes some of the key skills most children should master by a specific age.
There is a LookSee Checklist (formerly NDDS) for 13 key stages of development, from 1 month - 6 years of age. The checklists are available in English, French, Spanish, Chinese, Vietnamese, Arabic, Russian and Farsi.
If your child falls between two screen ages then use the earlier checklist e.g. if your child is 3.5 years of age then use the 3 year checklist.