As a segue to the eventual agreement to buy land, the letter of intent cobbles together the key points are to be finalized in the purchase agreement. While there is no specific form that the letter should take, you can state "Letter of Intent - Land Acquisition" at the top in block letters, date and address the letter to the party you are seeking agreement with, and highlight and/or enumerate the key terms in bold throughout the letter.
Lay out the key points and terms of the letter of intent. Specify who the buyer and seller are. Describe the property in question, including its address, parcel configuration and any water and mineral rights and leasehold estates associated with the land to be purchased. Establish the purchase price and when it is to be paid. State the condition of the land to be transferred, such as "as is." Note any earnest money deposits that are to be paid and how they are to be applied to the purchase price upon closing. Designate closing date, costs and brokers.
Outline due diligence procedures such as inspection periods, during which time the buyer is allowed to conduct routine inspections of the land within a designated time frame, such as 90 days. State how the buyer is able to terminate the purchase agreement during the inspection period without penalty and be entitled to a full refund of earnest monies. Cover related issues, such as the seller's responsibility upon execution of the purchase agreement, to furnish material studies, reports, tests and analyses to the buyer.
Discuss the pending purchase agreement. Designate that upon the fulfillment of the letter of intent, either the buyer or the seller must create the purchase agreement, which is to expand on the provisions of the letter of intent. State that the letter of intent does not constitute the full terms and conditions of the final purchase agreement, and the latter becomes effective upon the mutual execution of the agreement.
Note whether the letter of intent is to be binding, either in the section on the purchase agreement or at the close of the letter. Stipulate which parts of the letter are to be binding, or declare that the letter is not to be binding until a purchase agreement has been executed and delivered to both parties. Designate the extent to which the terms of the LOI will be applied to the purchase agreement, and whether the latter will supersede the LOI. Emphasize that the letter does not constitute a legal obligation and either party may terminate the negotiations for any or no reason -- otherwise the letter itself will terminate by a specified date.
State that if the above provisions are acceptable to the other party, that party should sign and date the LOI and return it to the undersigned -- you -- within five or some other set number of business days. Note that the LOI will expire if it is not signed and/or received during that time. Sign and date the document and provide space for the other party to do the same.