Mary ,
Apart from checking if it is a buildable lot (also does it front on a street or is it behind your home ? even in Island Park , the size might prevent a contractor from building anything ). If it is not buildable by itself, then about the only thing you can do is ,check and see if the lots on either side (yours included ) could be combined to increase the size and make a buildable lot ,
What I mean is , if the lot your home is on is say 120x60 and this lot is 50x60 then combined you would have 170x60 , and a contractor may be able to get variances to build on 2 lots or maybe your neighbor has
the same situation and combined you could come up with a buildable lot and get more money for it
But if not , then you have a great summer playground or , you could sell the lot to your neighbor , and he could use it for parties etc , but NOT for building , This would greatly decrease the value to a purchaser
so it would probably be best to keep it in that case .

First, go to your local building dept and find out if it is a buildable lot. That is the easy information...a town may allow a building lot, but the health dept may not. The more information you have, the easier it will be to give your property value.

Is this lot already subdivided from your property?

Contact me off line at Gail@GailGladstone.com with further info and I will be happy to try and give you a range.