I'm not big on rules but there are some basic courtesies that I try to observe for the benefit of others.
If I'm replying to a post with quotes, I try to snip the post to include only the specific points I'm replying to, particularly if it includes images. It's annoying to have to scroll through numerous copies of the same images, particularly to find a one-liner at the end of it.
I try to title new threads to provide some benefit to others. If the thread title accurately reflects the topic then it is easier to decide if it's something that you're interested in..
If I was to trawl through a serious of old posts in the same forum and reply to a dozen of them in quick succession it can have the effect of bumping other threads way down or even off the bottom of the page altogether if there are a lot of pinned topics. It's annoying to have spent time and effort putting something together only to have it bumped out of sight in this fashion. I don't do this.