First, wait until you're up to 100 Karma points.
Next, prep your house as follows:
1. Remove as many interior walls as you can. Walls act as firebreaks. The fire is more likely to spread throughout the house the fewer walls there are. This makes it unimportant where the fire actually starts.
2. Fill up your house with expensive stuff that burns easily. Expensive beds are a great choice. Wooden tables, bookcases, chairs, etc. are all good. Paintings and curtains are also good, especially since there are some expensive ones to choose from. Computers and electronics do burn, but I tried this achievement several times by stocking up on computers and never got it, whereas I got it easily with beds (specifically, the slave double bed) and paintings.
3. Leave plenty of floor space also. Floor space is very important. A meteorite won't start a fire if it hits an object; you'll only get a fire if the meteorite strikes the floor. Also, fires spread only via the floor.
4. Sell the fire alarm.
5. Get your Sims out of the house.
6. Remove all exits. (I had one attempt at this achivement ruined by a brave maid.) No one gets in.
At this point, do a save. Then start using the Firestorm power. You can use it up to 6 times if you have a full Karma meter. Hopefully, you'll get more than one good fire going. It will take a while for the fire to run its course. In that time, if midnight rolls around, you may get enough Karma points to use Firestorm again. Do it! (This ended up being a key factor for me winning the achievement.)
If the fire burns out and you don't get enough of a payout to unlock the achievement, reload your save and try again.
Good luck!