to find the hole if there is any bedding on the same. so, if your leaking air mattress has any bedding on it, then totally take off all this bedding from the mattress.
if you are lucky, then sometimes you can even determine the source of the leak on your air mattress with the naked eye. for this, you will need to allow more space for the mattress to be examined. so, if your room or area at where the air mattress is place is too confined for you to spread out the mattress, then it is better to move the mattress to a wider area at where you can spread 