Gaming Etiquette 101

So I  have been playing Team Fortress 2 a lot lately. I went from 1 type of of rocket launcher to four. And one thing kept popping up: poor gaming etiquette.
Well what do I mean by that? I mean spawn camping, text or voice harassing, and the list goes on. But for now, I'm going to talk about spawn camping.
Spawn camping is essentially, for those who don't know, is staying right near a spawn point and killing someone as soon as they spawn. Unless you're in a free for all server where there is no safe spot, you come off as a no skill jerk.
Sometimes its hard to tell if someone is spawn camping and if they're not. The lines sometimes blur especially in beginnings of maps. For the record, I'm using Team Fortress 2 as an example because I can get pictures easily of it. This isn't an end all guide of gaming etiquette, I'm just tired of trying to play a game but have no one even be able to get through the door.
Scenario #1
So I'm starting off at a map.

The game has already started. This is the area right out of the spawn camp. The other team can get in here, but unless we lost, you as another team have no right to be here. This is spawn camping.
Scenario #2

Here I am before a different map. This is an attack defend map. Slightly out of sight is the first map we have to capture. People defending this point are not spawn camping. They are defending. Payload maps also follow the same rule.
Scenario #3

My team's cart on a payload server is way ahead of the spawn point, if you can see the almost circular light blue shape in the background, that's our cart. These three guys are spawn camping, its way far away from their spawn and they're hitting us with rockets and ubercharges we're not ready for.

 There's no skill, there's no need, and you're not on your way to another point. It just makes you be this kid. No one wants to be this kid, because no one likes this kid.

Don't be the annoying childhood friend. Be a Good Guy Greg.