I think the parameters of trolling can best be defined as make a deliberately offensive or provocative online posting with the aim of upsetting someone or eliciting an angry response from them.
What actually is trolling?

To me, trolling is someone who just goes on the internet looking where he can cause trouble. Just constantly looking for trouble.
I think so many people get called trolls when they just say something and I don't think that is right. It needs to be someone looking for and then causing problems and just keeps doing it, just being a big jerk, probably because he has no friends or doesn't know what to do with himself. Has low self esteem, etc...

The term is subjective, but here's a definition (from that all-knowing oracle, Wikipedia):
In Internet slang, a troll is a person who sows discord on the Internet by starting arguments or upsetting people, by posting inflammatory, extraneous, or off-topic messages in an online community (such as a newsgroup, forum, chat room, or blog) with the deliberate intent of provoking readers into an emotional response or of otherwise disrupting normal on-topic discussion, often for their own amusement.

Used to be that a troll was known by another moniker in online gaming communities: "flamer". Haven't heard it used in a long time - Maybe because troll is a more politically correct label.

troll (trōl/)
a mythical, cave-dwelling being depicted in folklore as either a giant or a dwarf, typically having a very ugly appearance.
synonyms:goblin, hobgoblin, gnome, halfling, demon, monster, bugaboo, ogre

Trolling and flaming in the video game community is no better/more acceptable than it is here. If any a$$hats would start trash talking and flaming and baiting people on my Quake1 CTF server (guess that dates me...) they would be IP banned, first and last time for them. That is one reason my server was so popular.
In terms of who can be called a troll, I count 5 of them on this thread prior to my post (not that you would know purely by this thread's postings, of course). You can characterize them by their need for attention and the negative ways they go about getting it. Avatars that just scream "I need attention" are just a bonus indicator, OP.

Take a look at Ghostliner's definition of an Internet troll....I think whoever started this forum is a troll!!!😕

Its only the internet. Trolls only hurt people's feelings to encourage them to spend more time in the real world. The real world can be wonderful, but is also a very bad place for a lot of people who go through real suffering. Ask somebody starving to death if they care that somebody with luxury items got their feelings hurt by somebody on the internet. Trolls understand that you gotta have some thick skin to survive in this world. Some people are privileged and are weak themselves and they just want to start shit cuz they can't do it in the real world. There are punks in every genre. That's to be expected.
OK, so what really is trolling? The term seams very vague. Like if someone is being a jerk intentionally they are called a troll. Or people like me, who just like insulting people in fun (in the video game community, its normal to insult each other) are trolls as well. And when I am just being me and posting random junk, that's trolling as well! So what really IS trolling? I must know...