Some thoughts from someone who has spent a LOT of time in Yosemite (I live in Central Cali and most of our dayhikes and backpacking trips this year have been there):

* Rent a Wild Ideas Bearikade. You can do this by mail. It's easy and cheap. They will send it to you a few days before your trip, you return it in the box it arrived in when you get home. If you anticipate a LOT of future backpacking outings in black bear country, it would be my recommendation. I have a Bear Vault but am saving my nickels for the Bearikade. The ratio of can weight to volume is better, and the lid won't need replacing as bears figure it out - the Bear Vault has been breached in a couple of regions, and I recently had to upgrade my lid as the tab wasn't locking.

Be aware that it isn't just food that goes in. Your trash and your hygiene items, and the pills and ointments that might be in a first aid kit, all need to fit. I once had to stuff a sit pad I spilled olive oil over into a bear vault. If you have not packed a bear can before - repackage, take advantage of flat and round (tortillas or flatbread instead of muffins or bread), and favor the high calorie dense items.

Yosemite rangers are totally strict about food safety, read the website and take it seriously. Bears do really break into cars. A friend was escorted back to the trailhead for not having enough space in the bear can and hanging some of his stuff.

* I recommend to newbies to tackle Half Dome with care. 4,800 feet of elevation gain in one day is a lot, the trail is full of 5-6 inch dropoffs and rocks, and the days on the open areas going up to the falls (mist and vernal) can see temps upward of 85-90F - I know this is the "must do" trip everyone does, but so far as I am concerned it isn't worth your health.

To maximize safety and enjoyment, plan well ahead, faxing for reserved permits as early in the morning as you can (most people start at 12:01 am of the day permits first come available) for Happy Isles/Little Yosemite Valley as your first night destination. Those first come/first serve permits will go within five minutes of the office opening the day before the hike date. Spend the whole day walking if you have to, make camp, explore the river and even head up to Bunnell Cascades or fish. Get up early in the morning and hike the four mile round trip to the dome, spend as much time as you like up there. If your next night's destination is somewhere up the trail you will have all afternoon to get there - there's some good spots at the junction of the trail to Clouds Rest, or some people head up to Merced Lake where there is a High Sierra Camp. You can even get reservations in the restaurant there if you want - food's expensive but very good.

From Merced Lake you can go on to Vogelsang, out to Ireland Lake and beyond to Lyell Canyon, then up to Tuolumne Meadows. Or you could visit Sunrise Lakes and Cathedral Lakes on the way out. You could easily spend a night in the backpacker campground there and go up Lembert Dome, walk around Tuolumne Meadows, ride a shuttle to Tenaya Lake, then catch the hiker bus the next day around 2 pm back to the valley and your car.

To make this really easy for a bunch of newbies.... do it in reverse. Park in the valley, take the hiker bus to Tuolumne Meadows, and hike back to the valley by one of the several good routes - making much of the hike downhill. Visit Clouds Rest and Half Dome at your leisure. Then the permit would list either Sunrise or Cathedral trailhead, exiting at Happy Isles.

* Gear: You will need a 30F sleeping bag at minimum. Temps at elevation are going to drop, even in midsummer. We had a fellow on one of our hikes who thought, it's warm, I don't need my bag, and left it in the car - it was around 50F camping in the valley but in Little Yosemite Valley the following night it dropped to low 30s and he ended up awake all night trying to stay warm in a mylar blanket.

My favorite stove is my supercat - I use it with a .9 liter titanium pot for total stove/pot weight of about 5 oz. I boil water to rehydrate food. 8 oz of fuel (denatured alcohol or yellow HEET) was overkill for a five day trip I took recently. A canister stove like the pocket rocket or brunton is fine and the stove typically weighs about 3 oz.

The NeoAir is light, compact and comfortable. I went to hammocking because of comfort, and sometimes alpine hiking takes you beyond treeline, so picked up the NeoAir to try - I could not sleep on a regular Thermarest (as in, never actually went to sleep, lay there tossing and turning) - I did manage to get a few hours with the NeoAir. Nothing like the solid eight hours I get with the hammock, but far better than nothing at all. So if you are looking for a warm 13 oz alternative to the two pound DAM, that might be worth considering.

I would tweak all the gear and then look at packs in the 60 liter range to start. You'll need enough room for the bear can. I have a Nimbus Ozone (3800 - 4200 cu liters with an extension) and put the bear can upright in the pack, on top of my sleeping gear, stuffing tarp, hammock, jacket and tent stakes around the can. My day's food and rain gear ride on top along with the kitchen kit and water filter, and then the top of the pack is rolled down, cinched with a strap, and whatever socks or other laundry gets hung up to dry. My typical weight plus water is about 35 lbs.

You won't need the saw. Wood you can break with your hands is easy to come by, once you're out of the campgrounds. Above 9600 feet you won't be able to build a fire at all.

* Regarding elevation... if you aren't accustomed to hiking above 5,000 feet in elevation, read about altitude sickness and take appropriate measures as necessary. Camping a night or two at moderate (6,000 - 9,000) elevation before going over 10,000 feet is always a good idea, especially if you haven't routinely hiked at high elevation before. Half Dome is not terribly high at 8,836 feet, but it's the huge elevation gain within 8 miles that will make people suffer.