This is a fairly long article written by Michael Hobbes but really worth the read if you are interested in these issues. I have been hearing/reading a fair amount about foreign and domestic aid projects recently from both sides and I largely agree with this author's conclusions. These are my conclusions.
www.lowyinterpreter.org
There is no magic bullet.
One size does not fit all. What works in one instance can not be automatically scaled up and spread out everywhere with assumptions of the same results. Also there are differing measures of 'success'.
Donor expectations can easily exceed plausibility.
Even if you find the keystone change that may improve say, education, you can not anticipate all the long term and wide ranging adaptations of the community to this change. In other words the butterfly effects, positive and negative, are unpredictable.
Cultural legacies can not be ignored. This is true both at home and abroad. Asking local people what they want and need is key to understanding what is needed and what will really work there. Also keeping in contact and involving local people in long term follow up shows that you really care about more than just short term headlines.
And of course this is not to say that no one should try to help other people. It's still the right thing to do and some people are very passionate about it. Just be aware of the pitfalls and try to ensure what you're doing doesn't actually end up making those people you were trying to help worse off then when you started.