Voltage: 220-240 Volts (U.S./Canada are 110-120 Volts)
Primary Socket Types: British BS-1363, Indian
Multi-voltage appliances (laptops, etc.): Plug adapter
Click socket type links to view adapter for that type
110-120V electronics: Plug adapter + step-down transformer
Hair dryers, curling irons, etc.: Plug adapter + voltage converter
For the most part, there are two types of electrical sockets (outlets) used in Ghana: the "Type G " British BS-1363 and the "Type D" Indian (old British BS-546 5 amp "small") sockets. If your appliance's plug doesn't match the shape of these sockets, you will need a travel plug adapter in order to plug in. Travel plug adapters simply change the shape of your appliance's plug to match whatever type of socket you need to plug into. If it's crucial to be able to plug in no matter what, bring an adapter for both types.
Adapter for "Type G" British BS-1363
Adapter for "Type D" Indian BS-546 5 amp
But the shape of the socket is only half the story!
Electrical sockets (outlets) in Ghana usually supply electricity at between 220 and 240 volts AC. If you're plugging in an appliance that was built for 220-240 volt electrical input, or an appliance that is compatible with multiple voltages, then an adapter is all you need.
But travel plug adapters do not change the voltage, so the electricity coming through the adapter will still be the same 220-240 volts the socket is supplying. North American sockets supply electricity at between 110 and 120 volts, far lower than in most of the rest of the world. Consequently, North American appliances are generally built for 110-120 volts.
But that doesn't mean that your specific appliance isn't already compatible with the higher voltage -- it may very well be.