Overview with best arrangement for an 8 day, 7 night trip:
All information presented here is based on two trips in 2004

Day 1, 12 miles, 700' up, 2000' down:
Unless you've been there before, it is advisable to consult the rangers about the drive to the trailhead for Marvin Pass. I was handed a rough sketch, that proved indispensable.
Okay, shoulder the packs and head out, after making sure no trace of food is left in the vehicles (standard Sierra practice; bears). The whole area up here is wrangler territory. The trails are dusty and smelly with dull scenery and very few backpackers. This is the dud-day of the Colby route, so don't worry, things will improve vastly once reaching the Roaring River Ranger Station.
We always camped at the east end of Sugarloaf Valley, where Ferguson Creek provides a rare source of water. Decent campsites with no view, but so it goes.

Day 2, 10 miles, 2400' up:
This whole trip is characterized by hard, long days and this is another fine example. But now it gets interesting too.
Shortly after breakfast one passes right by the RR Ranger Station, which is usually deserted, because the Ranger there like to do her job, namely patrolling.
The trail soon enter amazing Cloud Canyon. From here all the way over to Junction Meadow, 20 miles distant, is the single best stretch of trail I've walked in the Sierras. Sure, others are grander, more spectacular, higher or steeper. But none combine such vastness and beauty with an overwhelming sense of solitude as does the Colby Pass trail.
When leading a big group it is a bit challenging to locate decent campsites at suitable distances for the whole puzzle to work out in the end. In this case Colby Lake is just too far for most people, although it is a great spot. Earlier, before the Whaleback, there's wet meadows whose fringe land have promising camps, but this is not far enough. Between those two options the trail is steep and rugged, with few possibilities except for very small groups. We ended up favoring the socalled Windy Bench, a rather indistinct collection of 5 tent platforms right off the trail, on the 9600' contour line. It is a stark, austere place of little cosiness, but leaves an impression. I got to like it. Can't speak for the clients.

Day 3, 10 miles, 2400' up, 2000' down:
Up, up, up. After lovely Colby Lake the climb to the pass gets very rugged, and steep too. Snow lingers here way into summer. Granite wasteland. This is a cruxy passage for many, and any trip leader will draw a deep sigh of relief when the group is finally seated for lunch at the top.
The descent is comparatively mellow. After some steep miles, the trail joins the Kern Kaweah River for its run down to Junction Meadow. A pretty lake named Gallats is passed and soon after a fine campsite straddling the trailshows up in the woods. It is not totally obvious so keep your eyes peeled.

Day 4, 10 miles, 2000' down, 2400' up:
The inverse of yesterday, and also quite hard.. First down to the Kern via some spectacular sections of trail. In one spot a ranger once lost her horse down a steep boulder filled chute. Must have been a bummer. At times it is far between water before joining the High Sierra Trail at Junction Meadow.
The hot afternoon couldn't be better spent than laboring up the long, sun drenched incline to Wallace Creek. This is one of my favorite hills. It is just the right angle for a good pace, it is long, the views are good and it signals the point where most people realize they've gotten their trail legs. But beware: The most severe case of heat exhaustion we ever experienced also occurred here. At Wallace Creek campsite our route convene with the super highway called the John Muir Trail, and puts an abrupt end to the solitude of the last 4 days.

Day 5, 7 miles, 1400' up, 300' down:
The easiest day on the trip.
After Wallace more ascending lead to an indistinct saddle, followed shortly by the first view of Mt. Whitney, if you know your mountains. Mere minutes ahead is the Ranger Station at Upper Crabtree.
Here a long midday break is in order since the short jaunt to desolate Guitar Lake will only take a few more hours. No need to arrive too early at this shadeless, exposed body of water under the southwest flank of Mt. Whitney, where the camps are on rock slabs and brown eroded grass. Neat spot though, once the sun gets low in the sky. If a thunderstorm pattern has set in, delay even further and plan to arrive after dinnertime, when most Sierra thunderheads have blown themselves to pieces. You don't want to be up there in a lightning event. This camp is at 11400', but everybody should be sufficiently acclimatized by now.

Day 6, 13.5 miles, 3000' up, 4000' down:
The recommended procedure is to climb Mt. Whitney day-hike style from Guitar Lake, leaving the bulk of your burden there. In the afternoon upon returning from the summit, strike camp and stroll down to Lower Crabtree Meadow for the night. Then hike back out to civilization via Cottonwood Pass and Horseshoe Meadow over the next 2 days.
This has several advantages over the traditional exit through Whitney Portal.
The first and most obvious is more time in the backcountry. Why rush back?
It also eliminates the herculean task of hauling all your gear up to 13500' at Trailcrest and, if conditions are unfavorable, there's no commitment to cross the main spine of the Sierras in order to get out. Just turn around and leave Guitar the way you came.
Finally, you avoid the craze of the east side of the mountain with all the day hikers and other mayhem, a considerable asset in itself.
Well, on to the climb: If you posses any kind of mountain sense, get up at 2 AM, and leave no later than 3. With a thunderstorm pattern in place or stragglers in you party, even earlier. Climbing a high peak (in our case the highest in the lower 48) is something that stirs a certain unease in me, even if it is just a walk-up like this one. An early start is the alpinist's traditional first line of defense in a hostile environment full of challenges. What might appear like an over cautious notion, is in reality the ingrained method of mountain folks through generations.
The first leg is to Trail Crest at 13500'. Here in the windy cold of high altitude is the spot where you will intersect with the day hikers. It is a 4 mile roundtrip with 1000' of gain to reach Mt Whitney from Trail Crest, and it is incredible exposed to bad weather. In deteriorating conditions (read: too late of a start), this is the the time to make the right decision.
After the glorious moments on top head on down the way you came up, naturally.
If you are savvy with the terrain and know what to look for, you can bag Mt. Muir right off the trail, via a bit of exposed 3-4th class scrambling. Likewise earlier on with Keeler Needle, which is a bit easier.
At Guitar pick up your stuff and, while basking in the glory of bagging a major peak (or two), stumble on down to Lower Crabtree Meadow, which is one of the finest camps on this entire trip. Whitney is a prominent feature of the view from here, and after 4 stays, I've yet to share it with other parties.
With guided groups this is at least a 14 hr day, including lunch and a nap at Guitar.
Expect to find no drinking water on this entire hike!

Day 7, 9 miles, 1000' up+down:
Slightly anticlimactic yet still a fine walk in the mountains, this 10 mile day has few highlights. Just do it, and be rewarded by another amazing camp at the unnamed lake right on the trail, a mile below Soldier Lakes. Elevation is 10450'.

Day 8, 11 miles, 1500' up, 800' down:
With the end in sight, it is easy to miss the unique scenery at this end of the range. It's dry here, with gnarled and weathered Foxtail Pines that look more dead than alive. The vistas are enormous, ranging from the distant Kaweahs, to the never ending blue ridges of the Golden Trout Wilderness. The trail is sandy and windswept as it follows the flank of a high ridge at or above 11000'. You know you're at the edge of the Great North American Desert here. This is amazing territory, and a fitting finish to one of the greatest walks around.
A slight descent takes you to Cottonwood Pass and the last miles down to the pavement.

Notes:
82 miles, 15000' up, about the same down.
Permits are required for this entry point, and they are subject to a quota system.
There are many camps along the way without permanent bear proof storage containers. Since slinging food from trees was always a pain, and occasionally failed, I started using personal bear canisters several seasons ago. This makes a high anxiety subject hardly an issue.
Ranger Stations enroute are Roaring River, Crabtree and Rock Creek. Even with these 3 nicely spaced outposts there's no doubt about the commitment to self rescue in the remote Colby Pass region. Also be aware that reaching one of these stations may not solve any of your problems, since the understaffed Rangers almost always are away on patrol.
If you do need emergency assistance in the remote Kern Canyon, the best option might be the very long slog south on fairly level terrain to Kern Station.
Cell phones are positively useless everywhere on this trail, except the summit of Whitney.
There are fewer cruxy creek crossings compared to the two other Trans Sierra Routes mentioned here. Still, from a guiding standpoint, these events always represent the greatest risk of injury as overloaded clients perform bonebreaking stunts to avoid getting their boots wet.
A persistent rumor circulating among well traveled backcountry aficionados hold that Cloud Canyon is haunted. Sadly I can't substantiate this.
The map of choice is a waterproof composite from Tom Harrison Maps, called Mt. Whitney High Country. This sheet, in 15 minute scale, cover all three routes with good detail. Contours are easy to read and trail information include mileage, ranger stations and spot elevations. Highly recommended.
Guidebooks? You just finished reading one. Please contact me with any comments.