Let's take a moment to think of what the description entails. It is not saying that you are an informative person (this is a given!), but that the information you are providing is useful to the reader. The best way to inform the public (on Slashdot, anyway) is the technique commonly referred to as "plagiarism", which is just a fancy-shmancy legal way to say "using other peoples' words without their knowledge or consent". Used correctly, this method will yield solid results.
An article on a topic you know almost nothing about (i.e., girls) has just been posted on Slashdot. It's been about a half hour since the last article was posted, so you are now Karma hungry.
What do you do, hot shot? WHAT DO YOU DO?!
Easy! Just search Google for "girls" and find what seems to be an intelligent post written by someone you don't know. Copy and paste without attribution, and huzzah, you now have "Informative" +1s coming your way like like moths to a bonfire.
Instead of a lame statement in a pathetic attempt to get "Funny" points, you now have an informed and literate ten-page dissertation on the topic, that sounds written by someone with a Master's Degree in Everything. The fact that you didn't write it should not mar your conscience; for all they know, the in-depth details of quantum isotropic modulation came from your brain!
You will sometimes have a reader recognize your borrowed information, and point this out in a reply with words like "plagiarist" and "lame" and "illegal". It should be evident that people who criticize you spend more time looking at message boards than in a mirror, so don't feel too bad. The proper response to annoyances like these will be discussed in a later chapter, "Flamebait".
Also troublesome is the person who will think you actually wrote your post, and replies asking for a clarification. Just ignore them, so they will think your time is WAY more important than replying to an obviously all-encompassing explanation of whatever topic you chose. It's not your fault if they're stupid.
Honing your copy-paste skills might take a while, but with a little discretion, care and taste, copying and pasting other peoples' words can be your fast track to Karma heaven.
Remember, nothing is illegal on the Internet!
Feel free to comment, and add your own suggestions.