Have you read the cycling information yet? It will give an answer to these questions that you have. Not that I mind answering. . .
Basically a cycling tank will go through these stages
- Ammonia = high, Nitrite = 0, Nitrate = 0
- Ammonia = mid-low, Nitrite = high, Nitrate = 0,
- Ammonia = low, Nitrite = mid-low, Nitrate = 0-low
- Ammonia = 0, Nitrite = low, Nitrate = low-mid
- Ammonia = 0, Nitrite = 0, Nitrate = mid
When stage 5 is reached, your tank is essentially cycled. This can take anywhere from weeks to months depending on your stocking, feeding, cleaning, external water source, etc. Until then you want to keep changing water, but doing minimal filter/gravel maintenance until your ammonia stays at zero and then you can go to a once/twice a week water change schedules. At least that's how I've always done it. I don't even touch a new filter for the first month or gravel vac as these are the places your bacteria is growing. Keep your feeding minimal and test before every water change. Which with your die off I would recommend as frequent as you can. Good luck, keep us posted =]