Oh! And to prepare it, you should lay it out on a tarp/sheet/whatever and let it air out for 24 hours to let the natural bacteria in it eat up some of the ammonia. I skipped this part, and it was a bad decision. Ammonia spiked like CRAZY and I wanted to add fish right away and couldn't. While it's laid out on the tarp, remove the big sticks. DO NOT rinse it.
ALSO, keep your soil layer shallow unless you have tons of rooted plants to prevent anaerobic pockets. I have had A LOT of issues with that and finally have settled it down by adding more rooted plants. My soil layer is about an inch and a quarter, with half an inch of sand on top. If I did it again, I'd keep it shallower. I've seen someone keep the soil shallow (like 3/4 inch) toward the front, and increase it to 1 - 1.5 inch towards the back where the tall, rooted plants will be. That seemed like a good idea to me.