During that 8-day period before your hike, do the "climb high, sleep low" pattern as much as possible. That means exercising at higher elevations and going back down to lower elevations to sleep. The reason for "sleeping low" is that while sleeping you are more apt to develop the dreaded pulmonary or cerebral edema.

Acclimatization varies a lot among individuals, though. Some years ago I took my youngest son and my daughter (17 and 18) on a car trip, first to Yellowstone, then to Denver to visit family and finally on a 5-day backpack in the Park Range near Steamboat Springs. I grew up in those parts and, even after living for many years at sea level, had no problems with the altitude. During the initial period (about a week) we hiked in Yellowstone, did lots of exercise walking around Denver and made a couple of trips into the Denver Mountain Parks, including an auto trip to the top of 14K Mt. Evans, where I made the kids scramble around the summit. Despite all this preparation, on the first night out on the trail, at about 10,500 ft., my daughter woke up in the middle of the night with shortness of breath. I gave her a couple of aspirin and lots of water and propped her into a relatively upright position, figuring that if she didn't improve in half an hour I'd pack up--even though it was midnight--and start down. Fortunately she went right back to sleep. However, we had to curtail the trip---we found a nicer and slightly lower spot to set up a base camp; my son and I dayhiked while she stayed around camp. Every time she tried to climb higher she started having troubles again. As long as she went no higher than about 10,200 ft. she was OK. Her brother, on the other hand, had no problems on an 9-mile dayhike in which we climbed to over 12,000 ft., although he was really tired (and took a long nap) when we got back to camp, while I felt just fine.

In other words, unless you've had previous high altitude experience, you don't know how you'll react until you get out there. Follow all the advice above about the period before the hike, extra hydration and taking it easy the first couple of days of the hike. If it's possible to sleep at lower elevations the first couple of days of the hike, do so. If you start getting a severe headache or breathing difficulties, descend immediately. You might consider a "plan B" for hiking at lower elevations, say 8,000-9,000 ft., just in case you encounter the same problems as my daughter. On the other hand, you may have no problems at all.