I previously discussed the care a business must take to avoid unknowingly creating an express warranty in favor of consumers. Different industries have different warranty requirements. This link from the FTC provides a lot of information on federal warranty requirements for businesspersons who provide consumer goods or services. It is just a guide for compliance; it is not exhaustive.
The most important thing is to be truthful in your advertisements. Do not say things you cannot prove, and do not mislead consumers. Most consumer products require you to designate whether you provide a "full" or "limited" warranty, or no warranty at all. In those cases, a full warranty requires: (1) no limitation on the duration of implied warranties; (2) that you provide warranty service to anyone who owns the product during the warranty period; (3) that you provide warranty service free of charge; (4) that you provide either a replacement or full refund if you cannot fix the product, and the consumer gets to pick; and (5) you do not require consumers to do anything as a precondition for receiving service, unless you can prove that any precondition is "reasonable."
If you do not offer all of those things, you have a "limited" warranty (again, in applicable situations involving consumer goods). As with any warranty, your decision to offer a full, limited or no warranty must be conspicuously disclosed.