To get to Koko Crater, take the bus that also goes to Hanauma Bay. From where you get off the bus, you must walk about 3/4 mile down a road to the trailhead, which is close to the baseball diamonds. Koko Crater is 1200', and the trail has no switchbacks. I am an experienced hiker, but this was the most strenous hike I have ever done. It is a totally awesome experience. You are hiking straight up old tram tracks that are still in place from the days when it was used by the military to haul supplies to the top of the crater. All the track and railroad ties are still there. A good part of it is likely at a 40 degree angle going up. Take water or sports drinks, and take a break when you need it. At the top you can see Hanauma Bay, so when you come down from Koko Crater, just cross the road over to see Hanauma Bay, viewable from the general visitors area for free, or $7 to go onto the beach. Also from the top of Koko Crater you can see the skyscrapers of Waikiki Beach area about 8 miles away, and can also see Diamond Head.