The objective theory of contracts states that a party's intention to enter into a contract is judged by outward, objective manifestations (words and conduct) as interpreted by a reasonable person in the offeree's position, rather than the party's secret, subjective intentions. This differs from a purely subjective approach, which would focus on what the parties actually thought, potentially leading to uncertainty and difficulty in enforcement.

The common law mirror image rule requires that the acceptance must precisely match the terms of the offer; any deviation constitutes a counteroffer. U.C.C. Section 2-207 modifies this for the sale of goods, particularly between merchants, by allowing a definite expression of acceptance to create a contract even with additional or different terms, unless those terms materially alter the agreement, the offer expressly limits acceptance to its terms, or the offeror objects.

Valid consideration is a bargained-for exchange of legal value, where each party gives up something of legal value (a right, a promise, or an act) in exchange for something of legal value from the other party. For example, if Sarah agrees to sell her used car to John for $5,000, Sarah's promise to transfer the car and John's promise to pay the money both constitute valid consideration.

Promissory estoppel, or detrimental reliance, allows a court to enforce a promise even without traditional consideration if the promisor makes a clear and unambiguous promise, the promisee reasonably and foreseeably relies on that promise to their detriment, and injustice can only be avoided by enforcing the promise. This might occur if an employer promises an employee a bonus upon retirement, and the employee retires in reliance on that promise.

The typical categories of contracts falling under the Statute of Frauds include contracts for the sale of land, contracts that cannot be performed within one year, contracts in consideration of marriage, contracts to answer for the debt of another, and contracts for the sale of goods priced at $500 or more. These contracts are generally required to be in writing to prevent fraudulent claims and provide more reliable evidence of the agreement's terms given their significance or duration.

Substantial performance occurs when a party has performed the essential purpose of the contract in good faith, but with minor deviations. The non-breaching party must still perform but may be entitled to damages for the minor defects. Material breach, on the other hand, is a significant failure to perform that defeats the essential purpose of the contract, allowing the non-breaching party to suspend their own performance and sue for damages.

The primary goal of compensatory damages is to compensate the non-breaching party for the loss suffered as a direct result of the breach, aiming to put them in the same economic position they would have been in had the contract been fully performed. The two main types are direct damages (loss of the bargain) and consequential damages (foreseeable losses resulting from the breach). A limitation on consequential damages is that they must have been reasonably foreseeable to the breaching party at the time the contract was formed.

Specific performance is an equitable remedy where a court orders the breaching party to fulfill their contractual obligations. It is typically granted only when monetary damages are inadequate to compensate the non-breaching party, such as in contracts for the sale of unique goods (e.g., rare artwork) or real estate, where each piece of property is considered unique.

An intended beneficiary is a third party whom the contracting parties intended to benefit directly from the contract and has the right to enforce the contract against the promisor. An incidental beneficiary, on the other hand, is a third party who may indirectly benefit from the contract but was not the intended recipient of that benefit and does not have the right to enforce the contract.