One good way to check is using the avpu responsiveness scale : [substeps] Alert: look to see if he is alert, with eyes open. Does he respond to questions? Verbal: ask simple questions, and see if he is able to answer them.
[header] How to evaluate for head injuries during first aid [title] Make sure the person is conscious. [step] While the person may still be awake, there can be other concerns. You'll want to check him quickly to see if he is alert and responsive.