Being polite and considerate are sometimes subjective concepts and difficult to describe in absolutes that everyone can understand. It would be good to point out to dispersed camping newbies that there are usually written RULES that cover areas where dispersed camping is allowed. Sometimes the rules are posted on a sign at the entrance, sometimes you have to check with the agency that's responsible for the area you're wanting to camp.
Typical rules would be things like: dispersed camping must be at least xx feet from the road, xx feet from any body of water, never in any marked restoration area. There will also be rules regarding trash disposal, use of latrines, grey water, ATV and firearm use, length of stay, etc. These types of rules are more absolute and can be enforced by the responsible agency. You need to know what they are before you camp.
I would also recommend that everyone using the public lands for dispersed camping be prepared to pick up a few pieces of trash left by those who are less responsible than most of us would be. I try to always take a plastic grocery bag with us when we go hiking around, and I'm usually glad I have it when I find someone's discarded water bottle or cheeto bag.
:):)