1. Offer. An offer can be oral or written as long as it is not required to be written by law. It is the definite expression or an overt action which begins the contract. It is simply what is offered to another for the return of that person's promise to act. It cannot be ambiguous or unclear. It must be spelled out in terms that are specific and certain, such as the identity and nature of the object which is being offered and under what conditions and/ or terms it is offered.
2. Acceptance. As a general proposition of law, the acceptance of the offer made by one party by the other party is what creates the contract. This acceptance, as a general rule, cannot be withdrawn, nor can it vary the terms of the offer, or alter it, or modify it. To do so makes the acceptance a counter-offer. Though this proposition may vary from state to state, the general rule is that there are no conditional acceptances by law. In fact, by making a conditional acceptance, the offeree is rejecting the offer. However the offerer, at his choosing, by act or word which shows acceptance of the counter-offer, can be bound by the conditions tendered by the offeree.
3. Consideration. Consideration for a contract may be money or may be another right, interest, or benefit, or it may be a detriment, loss or responsibility given up to someone else. Consideration is an absolutely necessary element of a contract. As a word of caution, it should be noted that consideration has to be expressly agreed upon by both parties to the contract or it must be expressly implied by the terms of the contract. A potential or accidental benefit or detriment alone would not be construed as valid consideration. The consideration must be explicit and sufficient to support the promise to do or not to do, whatever is applicable. However, it need not be of any particular monetary value. Mutual promises are adequate and valid consideration as to each party as long as they are binding. This rule applies to conditional promises as well. As additional clarification, the general rule is that a promise to act which you are already legally bound to do is not a sufficient consideration for a contract. The courts determine the application.
4. Capacity of the Parties to Contract. The general presumption of the law is that all people have a capacity to contract. A person who is trying to avoid a contract would have to plead his or her lack of capacity to contract against the party who is trying to enforce the contract. For example, he would have to prove that he was a minor, adjudged incompetent or drunk or drugged, and so forth. Often this is the most difficult burdens of proof to overcome due to the presumption of one's ability to contract.
5. Intent of the Parties to Contract. It is a basic requirement to the formation of any contract, be it oral or written, that there has to be a mutual assent or a "meeting of the minds" of the parties on all proposed terms and essential elements of the contract. It has been held by the courts that there can be no contract unless all the parties involved intended to enter into one. This intent is determined by the outward actions or actual words of the parties and not just their secret intentions or desires. Therefore, mere negotiations to arrive at a mutual agreement or assent to a contract would not be considered an offer and acceptance even thought the parties agree on some of the terms which are being negotiated. Both parties must have intended to enter into the contract and one can not have been misled by the other. That is why fraud or certain mistakes can make a contract voidable.
6. Object of the Contract. A contract is not enforceable if its object is considered to be illegal or against public policy. In many jurisdictions contracts predicated upon lotteries, dog races, horse races, or other forms of gambling would be considered illegal contracts. Yet in some states these types of contracts are valid. Federal and some state laws make contracts in restraint of trade, price-fixing and monopolies illegal. Therefore, a contract which violates those statutes would be illegal and unenforceable. This is true for drugs and prostitution or any other activity if considered criminal.