firstly, a bit of honesty on the part of the coalition would have been appreciated i think. messrs bush, blair and howard managed to subtly change their tune away from WMDs and terroristm as these justifications became more and more dubious - i'm not ruling them out btw, just questioning if they constituted sufficient and reliable evidence to wage war on another sovereign country. as you say, war is not pretty, so in this day and age i feel a country should have a fairly strong reason to start one, particularly setting the risky precedent of pre-emptive striking
ok, a bit of UN co-operation would have been appreciated. given the obstinacy of france, germany, russia and china, this was always going to be tough - but even in post-war iraq, the UN could be more of an influence politically than it is, rather than just on a (limited) humanitarian level. the unwillingness of the us to share power is understandable, but puts a significant strain on the limited goodwill of the non-coalition internation community and the iraqi people. A stronger UN presence might give the occupation somewhat more legitmacy, and facilitate a handover. That's speculation, but my feeling is that the stronger the connection the new government has with the us, the less popular support it will be able to garner.
To be honest with you, I don't know enough of the detail about Iraq, its people, its politics or its history to accurately say how the war could have been better done - no offence, but i doubt you or anyone else on the boards do either, because we simply don't have access to all the information you'd need.
However, my personal opinion is that even in the case that one of the multiple justifications supplied for the war at various times was a valid and reasonable one - i can sympathise with wanting to remove a thorn like saddam - i believe that it could have been done in such a way to less antagonise the international community and the iraqi people. To many people, the whole thing smacks of shiftiness and it has tarnished the US's image internationally in terms of cooperating with other people, and added more propaganda fuel to the terrorist cause. The invasion, were it justified better and more transparently, could feasibly have had more international support and thus the post-war period could be less traumatic. Better involvement of iraqis in the decision making process, even if it went against us interests, might have averted some of the insurgency.
Basically, i agree that some of the fallout, damage and casualties of the invasion and occupation were unavoidable, but i also think that some of it was avoidable through better planning and understanding of the situation. For example, some might consider it naive to assume or claim that a "beacon of democracy" can be quickly established in a country, a region!, where anti-us sentiment has been running high for some time, and to underestimate the scale and intensity of the resistance - shouldn't the world's best intelligence agencies be able to pick up these things, and have their respective governments not override them for poltical reasons?