<<How would you change the charter of the UN to make it more effective? >>
In all humility, I'd have to back off on that one. The greatest minds in international law worked on that Charter and made it.
There is, however, one glaringly obvious problem. The Security Council veto. It was originally put in on the insistence of the U.S.S.R. but in more recent years was used more by the U.S.A. (after years of denouncing it.) I think in the long run the veto has to go, but the so-called Great Powers will have to trust the institution a lot more than they do now, and of course that trust has to be earned. Also, the composition of the Security Council - - it has to have some flexibility as to status and veto. Some recognition that the Great Powers of 1944 may not always be in the same position of dominance as they once were.
I think the U.N. has to build from small success to small success, learning by doing, self-correcting through analysis of past actions. A culture of unregulated international violence that built up since prehistoric times isn't going to be cured by something that started in 1944. It's a long slow haul. I object to those who tear down the institution for partisan reasons and I think the worst of the bunch are the State of Israel and the fascists and militarists who currently control the U.S. government. The U.N. now is the world's best hope for a better tomorrow. The better kind of Americans know that and take pride in the fact that the U.S.A. was the prime mover in its foundation.
I also think too much is made of the "anti-Semitism" and "anti-Americanism" of the UN, and specifically the General Assembly. First of all, it's exaggerated, and secondly, this is a debating forum. Members ought to be encouraged to blow off steam. The object is to avoid war, so a certain amount of yelling, screaming and name-calling (even shoe-pounding) ought to be kept in perspective.