When doing macro photography, depth of field is always a critical issue. Sometimes even f/32 is not small enough to give you as much depth of field as possible. Or, you may be forced to use a larger aperture like f/8 or f/11 due to low light circumstances, and tiny subjects like this poison dart frog just won't be sharp enough.
The solution is to make the back of the camera, i.e. the plane of the digital sensor, as parallel as possible to the plane of the subject. That goes a long way to increasing depth of field. When the camera is aimed obliquely to the subject, you lose depth of field.
I took this image during one of my semi-annual frog and reptile workshops in St. Louis. The next one is at the end of January. Email me if you might be interested in participating (photos@jimzuckerman.com). Everyone gets awesome photographs.