The previous posts have covered most of the ways of arriving at the value of a piece of land. Tax Records and having it appraised are very good ways of coming up with a "estimated value". The size and location of the property have a lot to do with its value, zoning, and most importantly recent sales activity in the 08005 area will have a great deal to do with the market value.
Remember that the "actual market Value" based on recent sales can be different from the accessed value the township puts on a parcel.
Ultimately, recent sales, the amount of similar or better lots available on the market now, what a buyer is willing to pay and the seller is willing to take, will determine the selling price and therefore the value. Good Luck this is a great time to be a buyer!
If you need any further assistance, please fell free to contact me.