Let me just start off by saying I am NOT a professional, everything I'm about to tell you I know from experience (which is most cases is the best way to learn) and just because it works well for me doesn't necessarily mean it will work like that for you.
I'm going to break this down into three posts. Part one: Bleach. Part two: Dye. Part three: Tips, Tricks and Miscellany. As an intro I'll give you the basics about my hair so you can kind of get an idea - My hair is naturally a dark blond. It dries pin straight and is fairly thin. I have pretty greasy hair meaning to feel fresh and clean I have to wash it daily (not saying I do...we'll talk about that in about part 3. ;))
Now we'll hop right into it.
It's scary, of course it is. This is what could hurt your hair and leave it damaged. But it's also a necessary part of achieving a vivid color. You will need to bleach your hair even if it's fair to begin with. Bleaching your hair not only makes it lighter but makes it porous so the dye can be absorbed (which in turn makes it stay longer).
My bleach of choice is and always has been Beyond The Zone Radical Bleach Kit. It works like a charm. It works super fast on my hair but I recommend having a friend help you. By the time I'm done applying it I usually only have to wait eight minutes before my hair is nearly white and ready to rinse. I follow the directions on the package all except for the recommended time which in my opinion is extremely excessive. If you were to follow the time guidelines there is a very good chance your hair would be fried.
*Tip: don't wash your hair the day you plan on bleaching your hair! Let your hair get good and greasy before bleaching.
If you have dark hair (dark brown or black) then you're most likely not going to safely bleach your hair to a desirable color in one sitting. Don't be discouraged and most importantly never ever ever bleach on top of bleached hair. Meaning don't rinse your hair after bleaching and start all over again. Your hair will need a resting period and a few conditioning treatments before bleaching again. Most likely the easiest option will be to bleach, then dye your hair a color similar to what the bleach left you with and keep doing this over a period of time making sure to condition and baby your hair.
The first time I had my hair dyed pink, it was professionally done and we were bleaching out 5 years of black dye build-up. It took 4 sessions and a few months, which actually ended up being too quickly as during the last session my hair was fried. That was the first and last time my hair was ever significantly damaged.
Take your time lightening your hair! Seriously, all the work you did to get from black to pink (or whatever color) won't be so pretty when your hair is fried, looks like straw and feels gummy when wet.
Your hair does not have to be one even color after bleaching for it look great after dying. Just like "normal" hair colors, bright colors look best when they have more than one shade/aren't a flat color.
How light your hair needs to be depends on which color you're trying to achieve. The blue-ish tint that the bleach left my hair in the photo above was perfectly fine for dying my hair pink/purple but probably wouldn't have been acceptable for a shade of orange. Something to remember is that rules of color blending apply with hair dye too. The dark blue streaks the bleach left appeared purple when I applied pink dye to my hair.
After you bleach...
Did you reach desirable color? If so, then it's time to dye! Stay tuned for part 2: dye coming early next week!
Hair still too dark? Why not try dying it a darker color like Manic Panic's After Midnight Blue or Manic Panic's Purple Haze to give your brown hair a fun tint? Wait at least 2 weeks before bleaching again.
Bleaching to re-dye/touch up roots...
When your roots start to get long it's time to do a touch up. I like to wait until they're so long I can't stand looking at them. When you're just looking to touch up and not change colors you only need to bleach your roots. Refrain from applying bleach to all of your hair, it'll just be unnecessary damage.
When bleaching to change colors (after already having a semi permanent color) it's best to fade the color as much as possible before bleaching. Try taking a long, hot shower, soaking in the tub, or doing a conditioning cap (we'll cover this in part 3) to help. Remember your hair has already been bleached in the past and probably won't need to be processed quiet as long.