Using a clarifying shampoo (one without silicones) and a light conditioner works well, as silicones can weigh down fine hair. Also, try not to use too many hair products apart from at the roots, as they too will weigh down fine hair and make it look limp.
Oh, and velcro rollers are great for adding volume at the roots.
I have baby fine hair, which I have in a layered bob, and had coloured for the last 10 years or so, plus I use a hairdryer most days. If I use conditioner straight after washing, even just on the dry bits, I find it's still unmanageable, i.e. my layers are very whispy, although I have this great shine and softness but my hair just looks flat.
My tip is, use a mist spray to dampen your hair a while before you intend to wash it, then rub a little conditioner into the areas where you think it's needed most, leave it a while, then wash it later and you still get shine, but without the loss of body. I do this before I go to bed sometimes.
I have fine hair, and find it impossible to go a day without washing it, or risk that hideous greasy/flat look. Blow dry your hair try starting with your head upside-down to give more volume.
I have really fine hair and I use Bumble and Bumble thickening products - shampoo, conditioner and styling spray - they are FANTASTIC. It is a bit more expensive than normal shampoo and I buy mine from the hairdressers but I have seen it on ebay.
I went 23 years washing my hair with normal shampoo and I always had lank, flat hair that I had to wash all the time.
B&B products for fine hair is excellent - even the conditioner is developed to lift your hair and not be too heavy. I also find that I don't have to wash my hair everyday, which is great.
wash and dry your hair in the evening, blow drying upside down (use a leave in conditioner as well - there are some good volume ones out there). Go to bed and wake up in the morning to hair with a bit more oomph in it. I have the same problem and if I wash my hair during the day, it's flatter than roadkill within an hour or so.
One thing you can do if you have to wash your hair during the day is dry as suggested above and then tie into high, but loose, ponytail for few hours. Then let it down and style as usual.