Hi Crissy,
I know all about fine hair and the desire for a change from the flat look one gets from it. This can be a challenge to say the least.
First thing many stylists would suggest is a body perm. This is a long time commitment until it grows out so if you have never tried it, you may want to start with all the other methods of temporary curl.
You didn't say if you had all one length hair or any layering. I need to know if I am on track so I will start with a few questions. By "big hair" do you really mean volume so that grabbing it by the handfuls it feels much thicker? And also looks lots fuller with some body, loaded with waves like today's styles?
I will begin by referring you back to a post I just did on Vanessa Anne Hudgens in the "From Hairstyles Watch" category. There is a pic of her hairstyle there along with the advice I just gave in styling it that way. Please note that I mention that this method works well on medium length hair as well.
Vanessa Anne Hudgens' hairstyle
Hair shaping pastes, spray on 'root-lifters' and sometimes just good old-fashioned hair spray applied to the root area there at the scalp as the
first step to styling your hair, will all help give some 'lift' to alleviate flat hair. These products save your hair by giving you alternatives to what is called backbrushing, widely known as teasing the hair, for any height. Backbrushing is damaging to the hair and should never be done continuously.
Good luck and let me know how you make out. Especially if I have not guessed correctly as to your definition of 'big hair'.