Past consideration will be good consideration if three conditions are satisfied, one of which is that the parties understood from the outset that act was to be rewarded in some way.

Performance of existing legal duty is not sufficient consideration to receive money, except if it goes above and beyond the legal duty.

Performance of an existing contractual duty owed to a third party to the contract may amount to valid consideration for a new promise.

Performance of an existing contractual duty owed to the the other party will not be sufficient consideration in exchange for a promise form the other party for more money.

Exceeding contractual obligations will amount to consideration; however this is question of public policy and degree.

In cases where the defendant has received a practical or commercial benefit and where there is no evidence of duress or fraud, performance of contractual duties may amount to sufficient consideration.

Part payment of a debt is not usually consideration for a promise by creditor to forgo the balance due.

Part payment of a debt is not usually consideration for a promise by creditor to forgo the balance due except if it can be shown that something different was offered to the creditor which was accepted (different product or early repayment of a smaller sum).

Where a party to a contract has, by words or conduct, made a promise to the other to forgo a legal right , then once the other party has acted on it he will have a good defense to any claim brought by the promisor.

The promise to waive a legal right may be implied.

The promise must act on the promise, but this does not mean that it has to be to his detriment, all that is required is an alteration of action.

The promise only becomes final and irrevocable if the promisee cannot resume his position; otherwise the promisor can resile from his promise on giving reasonable notice.

Promissory estoppel cannot be used to bring a claim forward, it may only be used as a defense (i.e as a shield, not a sword)

For promissory estoppel to apply, must be inequitable/unjust for promisor to go back and insist his full legal rights; if it is not unjust, then promissory estoppel will not apply.

Promissory estoppel will usually suspend legal rights, but equity will require some notice or intimation together with a reasonable period for re-adjustment before the grantor is allowed to enforce his legal rights.