In the very least, your land contract should include the address of the property and a full legal description of the land. It should also include the down payment amount, purchase price, the number of payments that will be made, the monthly payment amounts, and any balloon payments that may be required. You may also consider creating and attaching an amortization schedule.
Side Note: While it's easy to assume that your property listings only belong on websites where tons of people are already there, I think it's also important not to overlook the value of having your listings in front of many different audiences. Even when an advertising outlet is less-recognized or newer to the market, it could still be worth your while to post your property information there.
Do you know if the developer had a local brokerage do the sales for the project you mention? You might want to contact the developer, but I'd also suggest you speak with a Realtor first to get a market analysis for the value of your property. Then decide if you want to put your property on the market or if you want to explore contacting either the developer or the owners of properties adjoining yours to see if there is interest.
Additionally, the land contract should indicate how many payments will be made, their due dates, grace periods (if applicable), fees for late payments, and how the buyer should deliver each payment. Under a land contract, buyers are usually treated just like a property owner, and will be responsible for paying property taxes, insurance, and any utility bills associated with the land use.
FindMyRoof does a pretty decent job of putting together a nice listing that gives all the basic details in an easy-to-follow format. It's not a terribly complex process to create a listing, and the site doesn't draw in a huge amount of traffic – but it is a relatively targeted audience of real estate buyers, which may make the site worth your time and consideration.
Market for Land is Less Active – The market for existing homes is almost always more vibrant than the land market. There simply are fewer numbers of buyers for vacant land than consumers looking for homes. Start marketing a new home listing and a new lot listing when both are desirable and priced well, and you generally can expect fewer contacts about the new lot listing.