Hey, great topic. Somewhere in those threads you linked (I forget where) you were musing over what to advise beginners on aggresiveness. IMO the very best thing you can tell a beginner is to constantly expand his list of 'things to do'. By this I mean he has to ask for the things he can do to improve his position at all times, what grips he should go for, what grips he should deny his opponent, etc. etc.
For example, if someone's been going for a few weeks, he might know from guard a few guard subs and sweeps. So he's rolling, and he thinks armbar? No, can't do that from here. Scissors sweep? Doesn't feel right. So he just sits there, and becomes 'passive'. He needs to know that even if he's not in a good place to go for a sub or sweep, what other things he can fight for. Having an aggressive mindset does you no good if your aggression is unfocused; you need to know what things to be going for.
For example, when I first started learning half-guard stuff, I learned a few sweeps and ways to take the back. But I didn't know yet how to make a half-guard good or not, so I could never get enough of my opponent's weight on or off me to make them work. Furthermore, I didn't know what to fight for, so I'd just lay there waiting for an opportunity that never came. After asking, I learned to go for that underhook, defend that cross-face, try to get myself lower towards my opponent's waist, etc. etc. Now, even if I'm not ready to go for the sweep yet, I'm always fighting in half-guard, because I know where I am in relation to where I want to be.
The interview with Marcelo Garcia that Andre quotes has been stolen from the Arte Suave DVD and put on youtube. Recreated here for your viewing pleasure:
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Bonus points if you spotted the omoplatas from side control and mount and reverse omoplata he gets while rolling.