The Nuuanu-Judd trail starts near JAG and takes one from a dirt parking lot along the Old Pali Road to the Makiki/Tantalus network of trails atop the ridge. To get to the trail, you'll have to cross the stream. Fortunately, I found a precariously- situated series of rocks to get across the stream; otherwise I'd have had to get my boots wet or shed them for the stream crossing.
The stream forded, the hike begins with a relaxing stroll through a forest of towering Norfolk pine trees. A series of switchbacks--25 in all according to Stuart Ball--will deliver you to the aforementioned ridgetop network.
Impatient and curious at times, I decided to take an alternate route on my first and only ascent up Nuuanu-Judd. Instead of ascending via the switchbacks, I followed a route that bee-lined up the ridge. This approach, strenuous and steep, was made a bit easier by handholds provided by the grove of bamboo lining most of the trail. After a while, the bamboo forest ended and I found myself scaling exposed rock faces, hauling my weary frame up with the help of cables, and scrambling on my hands and knees under fallen tree trunks blocking the trail.
Muddy and sweat-soaked, I arrived at the ridgetop after about an hour of climbing. From there, I found the main trail and descended via the two-dozen-plus-one switchback route.
If you hike Nuuanu-Judd, stick to the main trail and avoid the bee-line ascent unless you're an adventurous sort. And when you're done, take a refreshing swim in Jack Ass Ginger.