Welcome to the board! I have 3c/4a (I think) fine hair. It's taken me years to figure it out and I'm still learning. Right now my hair is about armpit length in the back.
1) I use Bantu regular relaxer on my hair. My hairdresser takes about ten minutes (total time) putting it on and getting it off. In the winter I relax my hair about every 7 to 8 weeks and in the summer about every six weeks (it grows faster in the heat). I usually walk out wet in a ponytail, sometimes I 'll let them blow dry it and rarely roller settings, since that takes an hour and half under the dryer. I've been going to a Dominican stylist here in Los Angeles who seems to understand that I have fine hair with semi resistant curl not coarse hair which is what every other hairdresser assumes that I must have.
2) I wash my hair with a gentle shampoo (right now Carol's Daughter's Herbal Shampoo Ylang ylang & Frankincense) at least twice a week. Water is the best form of moisture. And I Condition Wash the other days with Humectress by Nexxus, followed by biosilk serum on towel dried hair and pull back in a ponytail with a little bit of Carol's Daughter's Hair Milk on the ponytail.
3) Once a week, I deep condition with Rene Furterer's Karite (although I'm going to try Carol's Daughter's Shea Butter hair Smoothie 'cuz it costs less) for at least 20 minutes with heat, rinse and then moisturize condition with Humectress for at leat 20 minutes with heat, rinse, biosilk and ponytail, with CD's hair milk on ponytail.
4) If I style it, I airdry it in the ponytail without CD's hair milk (oils and creams weigh down and cause my fine hair to separate). Once it's dry I flat iron it. At night, I'll put a little Humectress on my hair pin it up in a bun with a hair clip and tie a silk scarf around it (not tight).
5) My wet ponytail style at night I spritz the ponytail with a mixture of distilled water and glycerin, slather on Ebene's shea butter cream and pin it up in a bun.
6) If I notice more breakage then usual, after a relaxer I'll do an Aphogee treatment, followed up with a Moisturizing Humectress treatment. Be careful with the Aphogee because it's a really strong protein conditioner and can be a bit much on fine hair. Which is why I only use it after a relaxer (but not after every relaxer, only when I think it's necessary - which could be once a year or even less) because my hair tends to break more when it's time for a touch-up.
6) No hair grease. Petroleum products don't moisturize, they only coat the hair and suffocate the scalp. I moisturize with Humectress, everyday.
7) I've also been Surging lately.
8) Pre shampoo treatments when I have time is Olive oil on dry hair with heat for about 15 minutes or so.
9) and lots of patience...
Good luck.