Without wanting to blind you with science, there are various ways in which a business is valued. Each business is unique and will have key elements that will effect its value.
These all need to be accessed in detail and include key customers/suppliers, contracts, products, market position and trading history/reputation to name but a few. Other more obvious elements include assets, property, stock-holding, cash and true trading net profit.
There are then the potential purchasers… it is fair to say that if your business suits another business and will compliment being added to an existing company or operator then this is often the best route to market and will ultimately lead to a smoother transaction and in many instances a better price.