My general methology with the nodes is to give them 1/3 to 1/2 the normal orb for a given aspect.
They are calculated points, and tend to be energy receptors/modifiers, rather than energy generators.
Also, as mentioned above, the south node takes the polar aspect, and when considering aspect orbs, I use the overall lowest orb. For example, if an inconjunct is made to the north node, a semisexitle is made to the south node. The orb (atleast in my opinion) for the semisextile is less than for the inconjunct, so I go with that orb, cut in half or so, for both ends of the aspect pattern.
I always display both ends of the axis (north/south) in the chart, I think it makes things more apparent
Also, I consider it very important to determine which end of the axis the aspect is applying to. That is, if the object in question is moving towards the north or south node. This shows if the aspect in question regards past karma or karma being built during this lifetime. Big distinction! Also important, don't forget that a retograde object will be moving backwards in the chart, and to take that into account if neccessary.