State that, no binding contract is to come into effect, except to the extent set out in the letter and that neither the letter nor any work done or payment made under the letter shall be deemed to be a waiver of the requirement to provide a binding contract. Finally, every effort should be made to finalise the contract as soon as reasonably practicable after the letter of intent has been signed.
Why would you ever have to sign any type of agreement before you ever see the terms. When shopping for a car would you sign a letter stating that you will buy a car for ุꯠᇸ and hand them your money hoping that they give you a new BMW when they deliver to you a 1975 Pinto? No of course you would not.