I'm sure I'm the worst possible person to give advice here (considering my scissor-happy past), but at least I've got experience.
1. Heavy-duty treatments do not work with my baby fine hair. CO, or too frequent conditioning result in overladen hair with lots of build-up. There is no point in having hair of any length if it does not look good, and fine hair treated to the point where it resembles a greaseball is just ugly.
Keep the hair clean and use conditioner where you need to: the ends. Use leave-ins instead of regular conditioner or masks, if need be.
2. Fine-haired people should pay more attantion to avoiding mechanical damage and heat damage. (Abbrasion, sharp combs, combs with too thick tines, BBBs - unless your hair is stick-straight -, flat irons and blowdryers.)
3. The updo that looks fab on someone with 2c / M/C /iii hair will not look the same on someone else with 1a / F /i/ii hair. High ponytails, or buns on top of the head, etc. - updos that leave the hairline visible - rarely look good on people with fine and/or thin hair. More relaxed styles, however, do.
4. Washing one's hair often is not a sin. Even if it happens every day. It just isn't.
I'm currently growing out my 2c / F /i/ii hair out for the umpteenth time, this time accepting the fact that haircare routines followed by people with more or coarser hair than mine do not suit me. Here's hoping I can make it this time.