Wiring on a bike breaks down into two major areas. There's the charging circuit and the rest of it. Unfortunately there are several types of charging circuit, so I'm not even going to attempt that in any kind of detail here. What I can try and do is to give a better understanding of what the types of charging circuit are doing.

Basically all charging circuits are either alternators (produce AC current) or dynamos (produce DC current), and either permanent magnet (have permanent magnets in them....) or field effect (use electro magnets). Essentially the difference between field effect and permanent magnet systems is that field effect systems require a battery to "activate" the magnets before the thing will generate any electricity, whereas permanent magnet set ups are going to generate eletricity as soon as they start spinning. This means that if you have a field effect magnet set up you will need a battery for the bike, if you have a permanent magnet set up you won't necessarily need a battery, though less effective set ups may still need a battery, or at least a capacitor to store some juice from the first kick. Be warned though, permanent magnet alternator set ups run without a battery may kill the regulator pretty quickly due to overheating it. Also bear in mind that the older type of electro-mechanical regulator (usually a tin box and needing a seperate rectifier, as opposed to a finned aluminium solid state one which incorporates the rectifier) isn't too clever and will assume there is a certain size of battery there. Some really clever people can reset these so they don't overcharge smaller batteries, I prefer to throw them away and use a solid state combined one. Less bits to mount, more reliable, and usually "clever" enough to tell it's charging a smaller battery.

Irrespective of whether you have an alternator or a dynamo it will need the regulator as the faster it spins the more electricity it makes. Permanent magnet set ups tend to use the regulator to convert "surplus" electricity to heat and so the regulator should be mounted some where that it's going to get some decent airflow. Field effect regulators can either limit the generators output by turning it in to heat or by switching off or reducing the current to the electro magnets.

An alternator set up will also have a rectifier to convert the AC output to DC, though this may be combined with the regulator into a single unit. Dynamos produce DC any way and so don't need a rectifier.

If you can get hold of an original wiring diagram it's not too difficult to pick out the actual wires that make up the charging circuit. Copying the diagram and then using typists correction fliud to "white" out the irrelevant wires makes it a lot clearer. From there you should be able to figure out which wire goes where as long as you're using the stock components. It's not a big step to actually hook all that up, which just leaves everything else, which is where I can be a bit more helpful