Your comment isn't very specific. I assume you are talking about a total loss auto? You could also be talking about a settlement for a bodily injury claim which is more of a judgment call.
For auto, you need to find several like automobiles (same condition and miles) in your area to use as documented proof of value. A car in California may be worth more than a car in Louisiana due to income levels in that area. A Blue Book price is respresentative of the country or region as a whole and may be over stating your area. A common practice of insurance companies is to say a vehicle is for sale at that price but probably sold for less. If you can find at least 3 other vehicles that are identical (at least within 5,000 miles or so) and verify the sold price, you could use that in small claims court and avoid a lawyer.