I have had my 20 gallon tank set up now for about 5 weeks (4 with fish) and I make suren to check levels everyday. My Ammonia spiked at just about (+\-) 2. And my Nitrite was at 2 untill today (it hit 3). I've been doing 10 to 15% water changes every day or every other day at the latest. I started with 2 Zebra Dinos and 2 golden Teters and they all 4 seem to be very active and happy. I just will be happy for the day my Nitrite tet at zero.
I've also started a fishless cycle on a 10 gallon tank. It's the long way around, but I figure no fish will suffer this way (just wish I've of know about the fishless cycle before I started the fish one).
I've talked to a few LFS and they all swear by bio-spira, the probelm is it's very hard to come bu here in Utah, not sure else where.
Just take it slow and if you do do a FISH cycle, be willing to change a lot of water and you just pull though it. I've heard it'll take longer do teh water changes, but I'd perfer my fish to make it.
Robb