However, it is easy to make mistakes when trying to follow these methods.
Here I explain a no-think lacing method which is really easy. In the example I change the hub of a wheel, but the same method may be used to copy the lacing pattern of an existing wheel when building a new one.
Spokes, rim, hub, as needed. You will provably need new spokes, which must be calculated for the hub and rim dimensions. Happily, spokes are cheap in internet and can be easily calculated online, for instance here: http://www.bikeschool.com/tools/spoke-length-calculator
Mark the side of the freewheel.
If you are building a new wheel, copy the numbers to the new rim. Pay attention to begin numbering next to the valve opening. The spoke holes in the rim are shifted to the side of the hub flange. Some rims may begin with the first hole shifted to right or to the left. If the new rim is not beginning towards the same side begin with the number one a hole further. The idea is to let the valve in a place with enough space to use a pump.
Enter the spokes in the rim holes having the same number. Screw the nipples, not tight, only some turns.