Sure, I'll gladly answer The things are easy once you know them, but can be confusing at the start. I remember how many times I had problems with it in the past... That's why I have put quotas there - I meant general instructions from USB Mode or H-E-N (I assume, that you're using USB Mode).
But, it's all not entirely related to hostmoding on N900. I meant that - in funny twist - those non-compliant hubs are better for N900, as they try to give peripherals connected to them as much current as needed, and can draw those power from N900's side (which can be already "augmented" with power from 3th branch of Y-cable) - which mean that those passive hubs act entirely like active hubs, for all intents and purposes.
Yes, see above. By the way, if you tinker with it a little, active hub can be powered from the same +5V power source as your N900 is charged from (via 3th branch of Y-cable) - this way, you can carry just one charger with you, instead of two. But for this, you need powerful enough +5V power source. I use a 2A +5V charger, that I have modified to contain two USB ports. I connect 3th branch of Y-cable to it (for charging N900), and another cable for powering active hub, to the 2nd port.