I submitted a couple essays and a spanish language evaluation through my university. In the second round I had a Skype interview with the country director for the specific country I applied to, where she told me what to expect in the field (bucket showers, no internet, spotty electricity, long hours... nothing I hadn't expected) and asked if I had any questions. The interview is mainly to make sure potential interns know this isn't a vacation. It's work, but it's really fulfilling.