Literally, the easiest way to do it is just to post in the Cyber Lounge. Most Cyber Lounge topics are fairly easy to reply/relate to. And it doesn't take a giant paragraph to explain them.
(Just make sure you don't revive any topic too old... that's against the rules as well)
Debate&Discuss area takes wayyyy too long to respond to. @_@ But it definitely has topics that have a lot of back&forth activity.
Sensory Pleasures, now there's a good section. An admin once told me that the "reviving dead topics" rule doesn't apply there. Not sure if that rule still is set, so you'll have to ask a mod if you want to be sure.

As long as it's any form of media, you can make TONS of topics in the Sensory Pleasures... and responding to some of them usually doesn't take too long.
... ^^; I got my Veterancy the long and hard way, don't know of any shortcuts. Sorry.