Wheel building puts many amateur motorcycle mechanics off because it looks so damn complex but broken down into bite size steps it's actually nowhere near as difficult as it might appear. Having built several spoked motorcycle wheels now, it genuinely does seem to get easier the more I do.
Undoubtedly everyone has their own way of doing this job and my methodology may or may not follow standard workshop practices but we can be assured the end results are correct; well, they work on my motorcycles anyway. I use the protocols and techniques passed on to my by father along with a few self-taught wrinkles; hopefully such combined wisdom will lay a few ghosts to rest and clarify the process. In a perfect world I'd have a wheel jig and wouldn't make mistakes. However I don't own such a device and do foul up; thus we learn.
The biggest problem would-be aspirant wheel builders experience is in understanding the basic layout of the rim, spokes and hub combined with their relationship to each other. Assume the hub has 18 holes on each flange/side; these will be at 20 degree intervals and nine will point one way and nine in the opposite direction. The holes one the other flange are generally 10 degree out of phase with their counterparts. The inner spoke from one flange sits next to the inner spoke from the opposite flange; ditto with the outer spokes. Each pair of inner or outer spoke dimples is pierced for a particular flange, although sometimes the angles are quite shallow and not immediately obvious.
Study an old wheel, or one from another motorcycle, and make notes or take photos to ensure you have an accurate map. A good point of reference is the valve hole; mark it with some tape and use it as a datum point. When it comes to fitting the outer spoke (from the inside of the hub) it's common for one or more spokes to be in the way. In this situation it's perfectly reasonable to temporarily remove any offending spokes and refit when the outer spoke is in place.
Wheels are perfect examples of symmetrical engineering and the number of spaces between inner or outer spokes is constant; use this as a key to successful spoke wheel building. Generally speaking, if the hub, rim and spokes are known to be correct and the build goes awry you've made a mistake somewhere. Typically it'll be something stupid such as starting off from the wrong point and then multiplying your errors as you go round. Take some time to relax and retrace your steps, it'll all make sense sooner rather than later.