2. Rosemary is great for dandruff. I've tried boiling some rosemary and spraying the water on my head. It works pretty well for mild dandruff and stops the itch for a while.
3. Wash your hair more? Though it is recommended to wash your hair once a week during the first stages, being a dirty, stinky, itchy dreadhead is no fun. If it gets bad, wash it, but try and hold back as much as you can.
You can help reduce dandruff torture by preparing before you get dreadlocks. Start skipping days a month or more in advance. Practice washing your hair when it feels dirty, not because it's a routine. If you can go over a week without washing (with normal hair) then you should be pretty set when you do get dreads.