First they give you an assignment that you have to do from home, time limit for the task is 2-3 days which can be easily done. After that you have a telephonic round with CTO who asks about your background, the domain you have worked and currently working on, some technical questions on .NET & SQL. After clearing the telephonic round you will be called at their office for other rounds. There will be another technical F2F round with the CTO. After that a non-technical round with the COO and salary negotiation. Be clear about your salary expectation, don't give in to what they say. They cannot offer much salary like tech companies since they are a NGO. So they will offer try to lure you in with whatever your current salary is plus a little extra which is performance linked variable. But we all know what "performance linked variable" is ;)