I served 20 years in the U.S. Air Force; as an airman, a non-commissioned officer, and finally, a commissioned officer. I gave and received criticism on a continual basis, but only just recently realized how this applies to the feedbacks unique to our hobby. We're a community of people first and foremost, and our hobby is supposed to be about getting together and having fun. But fun often requires a dose of criticism, and how we deliver this is important if we want to achieve our goals. Here's what I've learned by serving...
#1 LEAD BY EXAMPLE
I was a meteorologist commanding meteorologists. If I'd never taken a surface weather observation or prepared a forecast, I'd lack credibility to my team. Doing what I was asking others to do made them more likely to accept my critiques - and made me better able to formulate legitimate ones. Believe it or not, this applies to our hobby as well.
Running an adventure is one thing; playing is another, and some experience with the latter helps greatly with the former. Knowing how players think promotes better critiques because the GM can appreciate what people (and their characters) are reasonably capable of and what mistakes they can justifiably overlook. The result is fairer, more defensible judgements for everyone. Getting out from behind the GM screen and submitting to the adventures of others means doing what we ask of our friends, which builds trust.*
Reviews are a little different. We're all consumers of things; and even if we don't personally fashion them, we can still judge their utility. Even so, actually creating the sort of products we review doubtless results in better, more thoughtful (and insightful) evaluations.
#2 PRACTICE SERVANT LEADERSHIP
As commander, success meant elevating others. They still had to do the work and earn it; but my job included making it easier. Even when I had to discipline folks, it was because their continued service and success was valuable and deserved my support. In gaming, the GM serves their players with a fun narrative experience, which just happens to include killing their characters from time to time. The counsels of death and disappointment are much easier to accept when the GM makes it abundantly clear where their heart is.
Moreover, product reviewers are providing a public service; but they should also be concerned with improving the quality of offerings, especially in an industry like ours where peers generate content. In other words, a reviewer should want to like everything they critique and offer criticism as if they wish to help creators to be their best.
#3 DON'T BELITTLE OTHERS
The military is famous for Basic Training, where abuse is performance art. Sure; but this is carefully regulated and gets ditched after training because it's no good way to engender trust or earn the kind of respect needed to be heard. Unless you're just a servile doormat, overt belittlement triggers an involuntary, visceral response. Call me an asshole and mean it, and I guarantee I won't hear the legitimate good advice you follow up with...
I once had a GM who thought he was Mister Spock. He'd steeple his fingers, raise an eyebrow and smile coyly as the party struggled to figure out his puzzles. It might have been endearing if he wasn't so condescending. He'd complain about how stupid everyone was, lamenting that he didn't have smarter players to match his intellect. Soon enough he had no players at all, which was a shame because he was otherwise an accomplished GM.
I also read a recent review that ended with a profanity laden rant about how 90% of everyone failed to meet their refined standards. My heart bleeds. Good luck getting anyone, much less the publisher, to notice their otherwise legitimate criticisms. Of course, the publisher is missing out if they don't - but what a roadblock! The purpose of GMing or reviewing must never be to give the impression of arrogance, even when an individual is obviously committed to the rightness of their cause. Belittlement hobbles every worthwhile goal.
Let your players run a game and put you on the spot; strive to help others get better; respect your message enough not to belittle people. This is leadership. I don't always get it right; seriously, I could fill a phone book with my mistakes. But having the right ideals can surely help, and this isn't confined to the military either. We're all called to lead in various ways, whether working our jobs, parenting, or just being there for the people we love. Our games (and our relationships) demand no less. Hopefully, we make the most of our abilities...
*I know, I know. This can be difficult in certain groups. Just do your best.