Thanks for recommending good practices - they are very helpful. 

I find the concept of 'net effect' (medical model!) challenging in some areas that are not visible in a short duration. How would we measure the net effect if we have short-term empowerment programs or climate change interventions? I also find it difficult to generalize randomized control trials for the areas that have wide impacts, such as air or water pollution. We can have qualitative data justifying the effects. However, the evaluation may need to challenge the programs that look for a quick-fix for a long-term problem!