Lots of good texts out there.
Keep in mind that absent a written record it may be a most daunting task to prove the elements of a contract. Far more than just meeting of the minds
And 101 more wrinkles if you mean a contract which holds up in court
My basic "contracts" text in B school was about 600 pages and that just scratched the surface
The concept of "consideration" is not as simple as it sounds as it covers far more than "payment"
Of course the parties must have capacity to contract --or apparent authority --minors, imbeciles, incompetents,
And the substance of the deal must be legal and the parties legally able to perform same.
Last but not least the relevant state statutue of frauds probably requires that certain contracts must be in writing to be enforceable .