Things that I have learned:
cornrows will ruin your edges. Any tension or your edges will ruin your edges. You can have long hair, but a missing hair-line if you do a PS to tight and aren't mindful or what amount of tensions is appropriate.
Too many pulled back styles can also put tension on various places in your hair AND can cause the center/crown area of your hair to matt. For instance, many ladies mentioned how their hair always matts when they wet bun-the hair on the INSIDE of the bun will not be as stretched or elongated at the hair on the OUTSIDE, thus creating a giant ball of fuzz which you must go through and detangle. And we all know that constant detangling/manipulation = more breakage.
DO NOT WEAR YOUR HAIR IN A SHRUNKEN STATE. EVER. Unless you want SSK's, splits, tears, and extreme breakage when you finally go to wash it again.
Fine hair dreads and matts so easily, allowing it to simply "do what it do" is not an option if your goal is to achieve length.
DEPP CONDITION YOUR ROOTS, I tried this recently and it worked wonders. If your hair often matts at the roots when you do twists, braids, or any other type of ps then this may be a practice that you want to implement into your wash day.
As someone said earlier, pull your hair apart gently. Do not rake things through your hair before doing this crucial step, and make sure your hair is either saturated in a slippery oil or conditioner. Also, I know as naturals we practice starting from the ends of our hair and then work your way up, but for fine haired ladies the roots are JUST as important as the ends. The roots will determine how long your hair style will stay neat, how long before your next detangling session, how easily you can or cannot distribute product on your hair. Don't just give attention to the ends when you dc, moisturize, and seal. Give your roots some love. Just because they're the newest pieces of hair doesn't mean they should be left to fend for themselves.
Think of it in the terms of human age. Babies need to be nurtured and guided in order to grow up big and strong, and older people need proper care in order to slow down their deteriorating health. The same idea applies to your hair. Give your roots a fighting chance to eventually become the ends of your hair! If you treat it bad now, how healthy will it be when it grows out??
Do not wash your hair loose if you have HIGH DENSITY fine hair. It will tangle and fight once it gets to shoulder length and beyond. There are many different versions of washing hair in sections whether it be braids, twists, clips, or while you're in a ps already. Your hair needs to STAY STRETCHED so that it can be properly moisturized and avoid having gnarly ragged ends.
disclaimer: I am not a hair expert, but I have been natural for 5 years now with varying hair lengths and have experienced quite a few set backs. This advice is based on my experience, personal observations, and the advice I have received from other places.