Form 1040EZ and Form 1040A do not support Schedule A. If you filed your return using either of those forms, you took the standard deduction.
Form 1040 supports Schedule A. See Form 1040 line 40.
Standard deductions for tax year 2016 were as follows:
- Single/Married Filing Separate: $6300
- Head of household: $9300
- Married Filing Jointly: $12600
Depending on your filing status, if the standard deduction matches what is on your line 40, then you took the standard deduction.
If not, check to see if Schedule A is filled in your return and if the number flows to Form 1040 line 40, if so, you itemized deductions.