Child tax credit is $1000 for a dependent child under age 17 at year end. You must be claiming the dependency exemption.
You must have a tax liability to offset the credit. If you don't have a tax liability, you can't get the credit.
You may get "additional child tax credit" instead if your earned income was at least $3000.
Child tax credit may be phased out for taxpayers whose adjusted gross income is above the limit for your filing status.
The limits are:
$110,000 for married filing jointly
$75,000 for single or head of household
$55,000 for married filing separately
The credit is reduced $50 for every $1000 of income (or part thereof) over the limit.