Although the range of different types of contracts is quite vast, a common thread unites them: the basic elements of a contract, and what you need to prove in the event that the contract is breached.
What You Need to Prove in Order to Win a Breach of Contract Case in New York
In general terms, in order to establish a breach of contract claim under New York law, a plaintiff must prove the following 4 things:
(1) the existence of an (enforceable) agreement;
(2) that the plaintiff performed his end of the agreement;
(3) that the defendant breached the agreement; and,
(4) that the plaintiff sustained damages as a direct result of the defendant's breach.
Lest you think that 3 out of 4 "ain't too bad," let me disabuse you of that notion -
A plaintiff's failure to prove any one of these elements will almost certainly prove fatal to a breach of contract claim.
Some Common Problems in Winning a Breach of Contract Claim
1) Failure to Reduce the Agreement to Writing
Some types of agreements - but not all - must, as a matter of law, be reduced to writing in order to be enforceable. See, e.g., New York's Statute of Frauds, which provides a list of approximately 10 things that unless written, will be void, chief among them being a contract to pay compensation for services rendered in negotiating a loan, or in negotiating the purchase, sale, exchange, renting or leasing of any real estate or interest therein, as well as a contract that, by its terms, cannot be performed within one year.
2) Proving that the Parties Entered Into a Binding Agreement When the Defendant Denies It
Leaving aside that some agreements such as illegal contracts, are unenforceable on public policy grounds, the prong that most often dooms breach of contract cases is rather basic: Proving the existence of an agreement.
When the defendant denies the parties reached an agreement, the plaintiff is obligated to set forth the essential and specific terms of the agreement that the claim is based upon.
An Important Caveat
As a corollary to this rule, the following must be borne in mind: generalized breach of contract claims that are cast against a battery of defendants will fail unless the plaintiff can show a specific agreement with each defendant. In legalese, this is called "privity."
In other words, if I enter into an agreement with A Corp. to buy some widgets, and A. Corp. breaches the agreement, I have no inherent right to sue A. Corp.'s 5 other affiliates that weren't parties to the original contract, and did not tortiously interfere with or otherwise induce the breach of contract. See, e.g., Chen v. Street Beat Sportswear, Inc., 364 F. Supp. 2d 269, 294-95 (E.D.N.Y. 2005).