Fitting working lights to a model boat is often not the easiest of tasks. Many are placed in awkward positions, e.g. at the top of a tall thin mast. This will require good planning and thin cable, and if lights are going to be inaccessible after fitting then you are best advised to include them in a parallel circuit. That way if one does fail then the others will continue to work. One common way of reducing the number of wires needed in a mast installation is to make the mast of brass tube and use it as a common negative connection for every light. That way you need only a separate positive wire for each bulb or LED.
You need to plan how many separate circuits you want, because you will need a separate switch for each one. For example, you might want the navigation lights and mast lights on one circuit, while the bridge and interior lighting is on another. This is where twin or multiple switches (e.g. ACTion P44 or P62) are handy, in as much as you can operate two or more circuits from one channel.
The question then arises whether to use LED's or conventional bulbs. LED's have the advantage of a much longer operating life and lower current consumption (about a third of that needed for a Grain of Wheat bulb), but they usually require a series resistor to make them compatible with the supply voltage and they are only bright when viewed from quite a narrow angle, like in a spotlight. Component Shop’s catalogue has a very informative article on using LED's as well as a calculator for working out the value of series resistors. Internet tools are also available e.g.: http://www.muzique.com/schem/led.htm
Another option, especially for very small lights, would be to fit a powerful bulb or LED inside the model and run optical fibres from it to the sites of the lighting points.