Ok So this is what i know ( I change my hair Dead frequently to various colours) first of all what is your budget?
You'll need a really good conditioner, And i recommend Fudge Dinamite, it is really priccey however, but a good alternative is the treseme deep repair mask, and id use it EVERY time you wash your hair.
Angel is right, Head and shoulders is good for getting semi permanant dye out, and other than that, washing powder is as well, the only thing is this really does damage your hair, hence the need of a good shampoo,
For bleach, I havent had good results with many except Jerome russel, 12% volume. remeber to start with the tips and mid lengths though!!!!!! are it can be disasterous,
As for Dye... Directions is just conditioner with colour in!!! that is a fantastic dye, as is special Fx, I use directions- Famingo pink for florescent pink and pillerbox read for very red hair!!!
Make sure you have a shamppoo and conditioner for coloured hair, the Elvive is quite good, Use the Fudge/treseme after your usual conditioner.
Oooooh a better tip also.. Put a little of your dye in with your normal conditioner when you need to, it tops up your colour so you will only have to dye it once a month!!!
Hope ive helped a little hun
CJ XX