Legal contracts must contain elements like agreement between parties, consideration or exchange of value, contractual capacity of parties, legality of contract terms, and genuine assent without misrepresentation. Common types of contracts include rental agreements and mortgages. Negotiable instruments like checks have requirements like being in writing, containing an unconditional promise to pay, and being delivered to the payee. An organized filing system with labeled folders filed alphabetically can help manage personal records on topics like taxes, insurance, and household matters. Electronic tools like spreadsheets and databases also aid in record keeping.