You either draft a written offer yourself or you have a licensed real estate agent (preferably a Realtor) draft one for you and submit it to the seller or their agent for consideration. A verbal offer and acceptance is meaningless in real estate unless it is for a short term rental.
A purchaser shall have the right to cancel the contract until midnight of the seventh calendar day following the execution of such contract. If the seventh calendar day falls on a Sunday or legal holiday, then the right to cancel the contract shall expire on the day immediately following that Sunday or legal holiday.
Under an exclusive right-to-sell agreement, the listing firm is offered compensation in the event of a sale regardless of who procured the eventual purchaser.
Under the Cooling-Off Rule, your right to cancel for a full refund extends until midnight of the third business day after the sale.
Unfortunately, however, unless the seller specifically offers some sort of return policy or you're entering into a sales contract that allows for termination, there are limited laws providing buyers with the right to claim buyer's remorse.