1. Your oven should maintain the temperature you set it at within a 5 degree range. The burner turning off and then cycling back on every now and then is normal.
2. Do NOT preheat the cookie tray. Recipes take into account a room temperature tray.
3. Use only the heating element at the bottom for baking. The top element is only used for broiling.
4. For totally crispy cookies, use a crispy cookie recipe, or you could try baking them on the lowest rack setting in your oven.
5. More flour means a drier cookie, and one that will tend to fall part easier.
You might think about going to your local book store and ask about Baking Books. There are some very nice ones out there that aren't expensive and have easy instructions and good advise.