I'll disagree with the 5 minute rule. I prefer to take time to read over a post, especially if it might be taken the wrong way. So writing some replies takes 10 seconds, but some that are more important will take longer.

I try not to bother remarking on political or religious postings, because frankly, it's simply opinions, and everyone has the right to a differing opinion. Only when someone starts to say "Everything MUST go xxx" will I usually feel any urge to comment.

Not lying should be in all aspects of life really. It's much easier to keep track of one truth, than many lies. Unless your girlfriend asks if she looks fat or something that involves some polite fibbing, that is.