The Rongai Trail ascends Mt. Kili from the north side. It is an easy and relatively short walk, the alitude being the only challenge. I was with a 9-member French group - everyone made it to Uhuru Peak (5896m), but we all had splitting headaches and some had nausea due to the fast climb. (We passed a German group on this route - 6 out of 8 eventually reach Uhuru Peak.) There are no huts, so we had 24 porters to carry supplies, including a dining room tent and table (the French insist on eating well). 1 cook, 1 guide, and 4 assistants.
Our 9-person group spent the night at the excellent Babylon Hotel in Marangu (1400m). The next morning we took a 2 1/2 dusty and bumpy chartered bus ride to Nara Moru (1900m) on the north side of Kili and parked at the Rongai trailhead at 11h. (If you take this route, your guide will know the exact location.)
Up via Rongai Trail. Down via Marungu ("coca-cola") trail.
EDITORIAL COMMENT: I think ascending the Machame Trail and descending the Marangu Trail would be an ideal route. The Rongai Trail is OK, but the photos I have seen of Machame are spectacular! The Marangu Trail is also beautiful, though relatively crowded. I also think that camping is better than staying in the huts.
Day 1: Hike up the easy-to-follow Rongai Trail to "Cave 1" at 2700m. Camp. Excellent views of both Mawenzi Peak (5149m) to the east and Kibo Peak, our destination.
Day 2: Continue up the Rongai Trail to "Cave 3" (3800m). Camp.
Day 3: Continue up the Rongai Trail for 3 hours to "Outward Bound Hut" (4750m). Rest. Afternoon acclimization hike to 5000M. Rest and dinner.
Day 4: Midnight start. All night hike past Hans Meyer Cave to Gillman's Point. Arrival shortly before sunrise. Hot tea. Continue for 1-2 hours along south rim to Uhuru Peak. Return to Gillman's Point by same route. Descend to Kibo Huts (4700m) for a hot lunch. Continue for 15 kilometers in afternoon to Horombu Huts campground (3720m). Rest and eat. (NOTE: the porters traverse with all equipment from the Outward Bound Hut to Kibo Huts - they do not ascend Kibo.)
Day 5: Continue descent to Mandara Hut (2700m) for a hot lunch. Continue in afternoon to Marangu Gate. Spend the night at the Babylon Hotel (short bus ride from Marangu Gate).
Aspirin for the headache you will have after ascending in only 3 days!
INSPIRATION: our group passed a one-legged German fellow slowly ascending the Rongai Trail on crutches. It's something to think about when the going seems tough ...